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	$198.25	12.308%	$222.6506	$222.65	$222.65	$222.70
Purchase #2	$35.31	5.425%	$37.2256	$37.23	$37.25	$37.20
Purchase #3	$92.34	5.568%	$97.4815	$97.48	$97.50	$97.50
Purchase #4	$41.33	9.232%	$45.1456	$45.15	$45.15	$45.10
Purchase #5	$146.58	4.520%	$153.2054	$153.21	$153.20	$153.20
Purchase #6	$169.59	9.454%	$185.623	$185.62	$185.60	$185.60
Purchase #7	$128.50	6.560%	$136.9296	$136.93	$136.95	$136.90
7 purchase totals =	$811.90		$878.2613	$878.27	$878.30	$878.20