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	$158.61	4.142%	$165.1796	$165.18	$165.20	$165.20
Purchase #2	$158.72	8.155%	$171.6636	$171.66	$171.65	$171.70
Purchase #3	$95.41	11.667%	$106.5415	$106.54	$106.55	$106.50
Purchase #4	$35.45	7.797%	$38.214	$38.21	$38.20	$38.20
Purchase #5	$79.71	10.805%	$88.3227	$88.32	$88.30	$88.30
Purchase #6	$174.59	7.787%	$188.1853	$188.19	$188.20	$188.20
Purchase #7	$140.88	5.414%	$148.5072	$148.51	$148.50	$148.50
7 purchase totals =	$843.37		$906.6139	$906.61	$906.60	$906.60