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	$91.59	8.109%	$99.017	$99.02	$99.00	$99.00
Purchase #2	$36.27	13.311%	$41.0979	$41.10	$41.10	$41.10
Purchase #3	$27.53	4.482%	$28.7639	$28.76	$28.75	$28.80
Purchase #4	$97.39	12.180%	$109.2521	$109.25	$109.25	$109.30
Purchase #5	$37.93	7.319%	$40.7061	$40.71	$40.70	$40.70
Purchase #6	$93.41	3.313%	$96.5047	$96.50	$96.50	$96.50
Purchase #7	$18.77	13.850%	$21.3696	$21.37	$21.35	$21.40
7 purchase totals =	$402.89		$436.7113	$436.71	$436.65	$436.80