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	$88.82	4.872%	$93.1473	$93.15	$93.15	$93.10
Purchase #2	$34.47	7.377%	$37.0129	$37.01	$37.00	$37.00
Purchase #3	$156.69	3.355%	$161.9469	$161.95	$161.95	$161.90
Purchase #4	$211.43	13.281%	$239.51	$239.51	$239.50	$239.50
Purchase #5	$33.37	12.218%	$37.4471	$37.45	$37.45	$37.40
Purchase #6	$85.34	4.756%	$89.3988	$89.40	$89.40	$89.40
Purchase #7	$93.53	12.139%	$104.8836	$104.88	$104.90	$104.90
7 purchase totals =	$703.65		$763.3466	$763.35	$763.35	$763.20