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	$56.48	7.209%	$60.5516	$60.55	$60.55	$60.60
Purchase #2	$169.25	9.600%	$185.498	$185.50	$185.50	$185.50
Purchase #3	$52.76	10.821%	$58.4692	$58.47	$58.45	$58.50
Purchase #4	$237.52	9.435%	$259.93	$259.93	$259.95	$259.90
Purchase #5	$157.96	6.497%	$168.2227	$168.22	$168.20	$168.20
Purchase #6	$237.89	11.685%	$265.6874	$265.69	$265.70	$265.70
Purchase #7	$170.83	6.269%	$181.5393	$181.54	$181.55	$181.50
7 purchase totals =	$1,082.69		$1,179.8982	$1,179.90	$1,179.90	$1,179.90