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	$141.62	5.400%	$149.2675	$149.27	$149.25	$149.30
Purchase #2	$110.77	11.417%	$123.4166	$123.42	$123.40	$123.40
Purchase #3	$240.51	10.760%	$266.3889	$266.39	$266.40	$266.40
Purchase #4	$186.82	5.314%	$196.7476	$196.75	$196.75	$196.70
Purchase #5	$208.93	11.313%	$232.5663	$232.57	$232.55	$232.60
Purchase #6	$154.42	6.674%	$164.726	$164.73	$164.75	$164.70
Purchase #7	$104.56	11.311%	$116.3868	$116.39	$116.40	$116.40
7 purchase totals =	$1,147.63		$1,249.4997	$1,249.52	$1,249.50	$1,249.50