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	$168.34	13.521%	$191.1013	$191.10	$191.10	$191.10
Purchase #2	$197.82	10.396%	$218.3854	$218.39	$218.40	$218.40
Purchase #3	$57.28	4.524%	$59.8713	$59.87	$59.85	$59.90
Purchase #4	$144.67	5.652%	$152.8467	$152.85	$152.85	$152.80
Purchase #5	$87.50	5.203%	$92.0526	$92.05	$92.05	$92.10
Purchase #6	$92.78	3.225%	$95.7722	$95.77	$95.75	$95.80
Purchase #7	$110.91	5.268%	$116.7527	$116.75	$116.75	$116.80
7 purchase totals =	$859.30		$926.7822	$926.78	$926.75	$926.90