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	$7.36	9.435%	$8.0544	$8.05	$8.05	$8.10
Purchase #2	$80.91	5.621%	$85.458	$85.46	$85.45	$85.50
Purchase #3	$154.25	12.112%	$172.9328	$172.93	$172.95	$172.90
Purchase #4	$231.91	7.653%	$249.6581	$249.66	$249.65	$249.70
Purchase #5	$227.89	12.520%	$256.4218	$256.42	$256.40	$256.40
Purchase #6	$210.84	4.616%	$220.5724	$220.57	$220.55	$220.60
Purchase #7	$104.65	6.150%	$111.086	$111.09	$111.10	$111.10
7 purchase totals =	$1,017.81		$1,104.1835	$1,104.18	$1,104.15	$1,104.30