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	$34.62	9.336%	$37.8521	$37.85	$37.85	$37.90
Purchase #2	$71.58	4.803%	$75.018	$75.02	$75.00	$75.00
Purchase #3	$196.91	7.756%	$212.1823	$212.18	$212.20	$212.20
Purchase #4	$110.54	11.690%	$123.4621	$123.46	$123.45	$123.50
Purchase #5	$176.25	5.232%	$185.4714	$185.47	$185.45	$185.50
Purchase #6	$94.48	13.650%	$107.3765	$107.38	$107.40	$107.40
Purchase #7	$25.31	11.188%	$28.1417	$28.14	$28.15	$28.10
7 purchase totals =	$709.69		$769.5041	$769.50	$769.50	$769.60