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	$68.29	5.316%	$71.9203	$71.92	$71.90	$71.90
Purchase #2	$190.43	11.568%	$212.4589	$212.46	$212.45	$212.50
Purchase #3	$159.55	12.587%	$179.6326	$179.63	$179.65	$179.60
Purchase #4	$50.30	3.611%	$52.1163	$52.12	$52.10	$52.10
Purchase #5	$46.81	7.253%	$50.2051	$50.21	$50.20	$50.20
Purchase #6	$134.89	4.491%	$140.9479	$140.95	$140.95	$140.90
Purchase #7	$208.64	7.231%	$223.7268	$223.73	$223.75	$223.70
7 purchase totals =	$858.91		$931.0079	$931.02	$931.00	$930.90