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	$159.45	5.842%	$168.7651	$168.77	$168.75	$168.80
Purchase #2	$53.36	3.135%	$55.0328	$55.03	$55.05	$55.00
Purchase #3	$111.76	10.542%	$123.5417	$123.54	$123.55	$123.50
Purchase #4	$122.74	13.357%	$139.1344	$139.13	$139.15	$139.10
Purchase #5	$93.86	10.721%	$103.9227	$103.92	$103.90	$103.90
Purchase #6	$243.96	8.201%	$263.9672	$263.97	$263.95	$264.00
Purchase #7	$200.58	4.389%	$209.3835	$209.38	$209.40	$209.40
7 purchase totals =	$985.71		$1,063.7474	$1,063.74	$1,063.75	$1,063.70