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	$184.56	12.760%	$208.1099	$208.11	$208.10	$208.10
Purchase #2	$37.90	9.732%	$41.5884	$41.59	$41.60	$41.60
Purchase #3	$179.34	4.698%	$187.7654	$187.77	$187.75	$187.80
Purchase #4	$141.37	10.131%	$155.6922	$155.69	$155.70	$155.70
Purchase #5	$147.36	3.422%	$152.4027	$152.40	$152.40	$152.40
Purchase #6	$84.77	4.463%	$88.5533	$88.55	$88.55	$88.60
Purchase #7	$233.74	13.318%	$264.8695	$264.87	$264.85	$264.90
7 purchase totals =	$1,009.04		$1,098.9814	$1,098.98	$1,098.95	$1,099.10