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	$139.72	5.278%	$147.0944	$147.09	$147.10	$147.10
Purchase #2	$148.38	8.689%	$161.2727	$161.27	$161.25	$161.30
Purchase #3	$116.50	9.814%	$127.9333	$127.93	$127.95	$127.90
Purchase #4	$54.87	13.224%	$62.126	$62.13	$62.15	$62.10
Purchase #5	$220.50	7.598%	$237.2536	$237.25	$237.25	$237.30
Purchase #6	$218.38	3.180%	$225.3245	$225.32	$225.30	$225.30
Purchase #7	$180.95	5.713%	$191.2877	$191.29	$191.30	$191.30
7 purchase totals =	$1,079.30		$1,152.2922	$1,152.28	$1,152.30	$1,152.30