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	$127.41	12.433%	$143.2509	$143.25	$143.25	$143.30
Purchase #2	$17.40	7.832%	$18.7628	$18.76	$18.75	$18.80
Purchase #3	$195.62	9.333%	$213.8772	$213.88	$213.90	$213.90
Purchase #4	$148.74	3.142%	$153.4134	$153.41	$153.40	$153.40
Purchase #5	$53.59	13.366%	$60.7528	$60.75	$60.75	$60.80
Purchase #6	$53.77	9.816%	$59.0481	$59.05	$59.05	$59.00
Purchase #7	$131.73	8.664%	$143.1431	$143.14	$143.15	$143.10
7 purchase totals =	$728.26		$792.2483	$792.24	$792.25	$792.30