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	$96.85	7.378%	$103.9956	$104.00	$104.00	$104.00
Purchase #2	$115.33	13.363%	$130.7415	$130.74	$130.75	$130.70
Purchase #3	$73.36	5.688%	$77.5327	$77.53	$77.55	$77.50
Purchase #4	$245.70	3.130%	$253.3904	$253.39	$253.40	$253.40
Purchase #5	$69.34	11.198%	$77.1047	$77.10	$77.10	$77.10
Purchase #6	$148.34	11.481%	$165.3709	$165.37	$165.35	$165.40
Purchase #7	$225.93	12.155%	$253.3918	$253.39	$253.40	$253.40
7 purchase totals =	$974.85		$1,061.5276	$1,061.52	$1,061.55	$1,061.50