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	$51.71	6.173%	$54.9021	$54.90	$54.90	$54.90
Purchase #2	$169.28	13.371%	$191.9144	$191.91	$191.90	$191.90
Purchase #3	$226.25	9.562%	$247.884	$247.88	$247.90	$247.90
Purchase #4	$79.75	13.603%	$90.5984	$90.60	$90.60	$90.60
Purchase #5	$249.82	11.588%	$278.7691	$278.77	$278.75	$278.80
Purchase #6	$139.97	10.753%	$155.021	$155.02	$155.00	$155.00
Purchase #7	$77.56	10.311%	$85.5572	$85.56	$85.55	$85.60
7 purchase totals =	$994.34		$1,104.6462	$1,104.64	$1,104.60	$1,104.70