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	$188.90	10.625%	$208.9706	$208.97	$208.95	$209.00
Purchase #2	$185.58	8.229%	$200.8514	$200.85	$200.85	$200.90
Purchase #3	$6.38	8.365%	$6.9137	$6.91	$6.90	$6.90
Purchase #4	$117.60	6.193%	$124.883	$124.88	$124.90	$124.90
Purchase #5	$33.84	10.216%	$37.2971	$37.30	$37.30	$37.30
Purchase #6	$33.57	11.745%	$37.5128	$37.51	$37.50	$37.50
Purchase #7	$100.43	7.831%	$108.2947	$108.29	$108.30	$108.30
7 purchase totals =	$666.30		$724.7233	$724.71	$724.70	$724.80