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	$88.67	12.796%	$100.0162	$100.02	$100.00	$100.00
Purchase #2	$106.61	5.566%	$112.5439	$112.54	$112.55	$112.50
Purchase #3	$162.42	12.133%	$182.1264	$182.13	$182.15	$182.10
Purchase #4	$125.28	4.363%	$130.746	$130.75	$130.75	$130.70
Purchase #5	$133.62	9.253%	$145.9839	$145.98	$146.00	$146.00
Purchase #6	$152.35	8.590%	$165.4369	$165.44	$165.45	$165.40
Purchase #7	$177.66	12.827%	$200.4484	$200.45	$200.45	$200.40
7 purchase totals =	$946.61		$1,037.3017	$1,037.31	$1,037.35	$1,037.10