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	$37.49	3.413%	$38.7695	$38.77	$38.75	$38.80
Purchase #2	$103.58	7.489%	$111.3371	$111.34	$111.35	$111.30
Purchase #3	$164.70	6.546%	$175.4813	$175.48	$175.50	$175.50
Purchase #4	$78.75	4.191%	$82.0504	$82.05	$82.05	$82.10
Purchase #5	$66.40	7.474%	$71.3627	$71.36	$71.35	$71.40
Purchase #6	$34.41	12.601%	$38.746	$38.75	$38.75	$38.70
Purchase #7	$221.49	12.132%	$248.3612	$248.36	$248.35	$248.40
7 purchase totals =	$706.82		$766.1082	$766.11	$766.10	$766.20