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	$161.28	3.488%	$166.9054	$166.91	$166.90	$166.90
Purchase #2	$123.74	6.577%	$131.8784	$131.88	$131.90	$131.90
Purchase #3	$36.77	8.376%	$39.8499	$39.85	$39.85	$39.80
Purchase #4	$190.26	4.236%	$198.3194	$198.32	$198.30	$198.30
Purchase #5	$97.67	10.689%	$108.1099	$108.11	$108.10	$108.10
Purchase #6	$165.50	3.528%	$171.3388	$171.34	$171.35	$171.30
Purchase #7	$121.72	8.569%	$132.1502	$132.15	$132.15	$132.20
7 purchase totals =	$896.94		$948.5520	$948.56	$948.55	$948.50