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	$111.98	5.466%	$118.1008	$118.10	$118.10	$118.10
Purchase #2	$213.95	3.449%	$221.3291	$221.33	$221.35	$221.30
Purchase #3	$68.88	4.705%	$72.1208	$72.12	$72.10	$72.10
Purchase #4	$205.68	9.125%	$224.4483	$224.45	$224.45	$224.40
Purchase #5	$33.38	9.359%	$36.504	$36.50	$36.50	$36.50
Purchase #6	$54.59	6.843%	$58.3256	$58.33	$58.35	$58.30
Purchase #7	$66.73	5.662%	$70.5083	$70.51	$70.50	$70.50
7 purchase totals =	$755.19		$801.3369	$801.34	$801.35	$801.20