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	$73.53	8.424%	$79.7242	$79.72	$79.70	$79.70
Purchase #2	$72.36	13.664%	$82.2473	$82.25	$82.25	$82.20
Purchase #3	$171.55	11.188%	$190.743	$190.74	$190.75	$190.70
Purchase #4	$83.68	3.234%	$86.3862	$86.39	$86.40	$86.40
Purchase #5	$31.51	5.849%	$33.353	$33.35	$33.35	$33.40
Purchase #6	$217.43	12.754%	$245.161	$245.16	$245.15	$245.20
Purchase #7	$17.52	5.746%	$18.5267	$18.53	$18.55	$18.50
7 purchase totals =	$667.58		$736.1414	$736.14	$736.15	$736.10