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	$82.67	13.603%	$93.9156	$93.92	$93.90	$93.90
Purchase #2	$165.32	6.435%	$175.9583	$175.96	$175.95	$176.00
Purchase #3	$176.91	12.840%	$199.6252	$199.63	$199.65	$199.60
Purchase #4	$119.74	3.222%	$123.598	$123.60	$123.60	$123.60
Purchase #5	$86.79	4.344%	$90.5602	$90.56	$90.55	$90.60
Purchase #6	$68.34	9.325%	$74.7127	$74.71	$74.70	$74.70
Purchase #7	$90.84	10.766%	$100.6198	$100.62	$100.60	$100.60
7 purchase totals =	$790.61		$858.9898	$859.00	$858.95	$859.00