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	$248.99	6.375%	$264.8631	$264.86	$264.85	$264.90
Purchase #2	$200.33	4.598%	$209.5412	$209.54	$209.55	$209.50
Purchase #3	$18.62	10.294%	$20.5367	$20.54	$20.55	$20.50
Purchase #4	$218.95	3.147%	$225.8404	$225.84	$225.85	$225.80
Purchase #5	$249.28	10.207%	$274.724	$274.72	$274.70	$274.70
Purchase #6	$45.69	7.615%	$49.1693	$49.17	$49.15	$49.20
Purchase #7	$57.69	4.589%	$60.3374	$60.34	$60.35	$60.30
7 purchase totals =	$1,039.55		$1,105.0121	$1,105.01	$1,105.00	$1,104.90