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	$211.93	8.731%	$230.4336	$230.43	$230.45	$230.40
Purchase #2	$103.56	13.760%	$117.8099	$117.81	$117.80	$117.80
Purchase #3	$152.36	6.869%	$162.8256	$162.83	$162.85	$162.80
Purchase #4	$216.48	4.363%	$225.925	$225.93	$225.95	$225.90
Purchase #5	$85.58	7.607%	$92.0901	$92.09	$92.10	$92.10
Purchase #6	$35.82	3.531%	$37.0848	$37.08	$37.10	$37.10
Purchase #7	$42.61	13.591%	$48.4011	$48.40	$48.40	$48.40
7 purchase totals =	$848.34		$914.5701	$914.57	$914.65	$914.50