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	$153.65	3.281%	$158.6913	$158.69	$158.70	$158.70
Purchase #2	$112.90	4.127%	$117.5594	$117.56	$117.55	$117.60
Purchase #3	$103.38	7.258%	$110.8833	$110.88	$110.90	$110.90
Purchase #4	$59.49	9.772%	$65.3034	$65.30	$65.30	$65.30
Purchase #5	$174.27	4.535%	$182.1731	$182.17	$182.15	$182.20
Purchase #6	$65.37	9.399%	$71.5141	$71.51	$71.50	$71.50
Purchase #7	$159.72	12.386%	$179.5029	$179.50	$179.50	$179.50
7 purchase totals =	$828.78		$885.6275	$885.61	$885.60	$885.70