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	$48.26	13.506%	$54.778	$54.78	$54.80	$54.80
Purchase #2	$154.85	7.319%	$166.1835	$166.18	$166.20	$166.20
Purchase #3	$42.98	7.525%	$46.2142	$46.21	$46.20	$46.20
Purchase #4	$99.94	11.612%	$111.545	$111.55	$111.55	$111.50
Purchase #5	$190.59	4.827%	$199.7898	$199.79	$199.80	$199.80
Purchase #6	$61.38	13.681%	$69.7774	$69.78	$69.80	$69.80
Purchase #7	$132.69	13.334%	$150.3829	$150.38	$150.40	$150.40
7 purchase totals =	$730.69		$798.6708	$798.67	$798.75	$798.70