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	$125.97	10.862%	$139.6529	$139.65	$139.65	$139.70
Purchase #2	$213.59	4.523%	$223.2507	$223.25	$223.25	$223.30
Purchase #3	$82.40	13.237%	$93.3073	$93.31	$93.30	$93.30
Purchase #4	$174.48	4.759%	$182.7835	$182.78	$182.80	$182.80
Purchase #5	$131.46	11.517%	$146.6002	$146.60	$146.60	$146.60
Purchase #6	$162.83	7.187%	$174.5326	$174.53	$174.55	$174.50
Purchase #7	$215.27	7.375%	$231.1462	$231.15	$231.15	$231.10
7 purchase totals =	$1,106.00		$1,191.2734	$1,191.27	$1,191.30	$1,191.30