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	$53.48	13.737%	$60.8265	$60.83	$60.85	$60.80
Purchase #2	$79.42	3.302%	$82.0424	$82.04	$82.05	$82.00
Purchase #3	$12.71	7.352%	$13.6444	$13.64	$13.65	$13.60
Purchase #4	$237.85	5.161%	$250.1254	$250.13	$250.15	$250.10
Purchase #5	$225.39	8.830%	$245.2919	$245.29	$245.30	$245.30
Purchase #6	$225.98	12.512%	$254.2546	$254.25	$254.25	$254.30
Purchase #7	$148.93	11.199%	$165.6087	$165.61	$165.60	$165.60
7 purchase totals =	$983.76		$1,071.7939	$1,071.79	$1,071.85	$1,071.70