Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$164.64	11.693%	$183.8914	$183.89	$183.90	$183.90
Purchase #2	$224.55	13.391%	$254.6195	$254.62	$254.60	$254.60
Purchase #3	$212.33	13.152%	$240.2556	$240.26	$240.25	$240.30
Purchase #4	$93.32	13.131%	$105.5738	$105.57	$105.55	$105.60
Purchase #5	$169.57	7.742%	$182.6981	$182.70	$182.70	$182.70
Purchase #6	$234.72	5.807%	$248.3502	$248.35	$248.35	$248.40
Purchase #7	$250.56	13.705%	$284.8992	$284.90	$284.90	$284.90
7 purchase totals =	$1,349.69		$1,500.2878	$1,500.29	$1,500.25	$1,500.40