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	$91.75	3.436%	$94.9025	$94.90	$94.90	$94.90
Purchase #2	$137.48	9.832%	$150.997	$151.00	$151.00	$151.00
Purchase #3	$54.55	13.798%	$62.0768	$62.08	$62.10	$62.10
Purchase #4	$242.97	8.288%	$263.1074	$263.11	$263.10	$263.10
Purchase #5	$232.54	9.105%	$253.7128	$253.71	$253.70	$253.70
Purchase #6	$185.58	3.170%	$191.4629	$191.46	$191.45	$191.50
Purchase #7	$33.97	11.308%	$37.8113	$37.81	$37.80	$37.80
7 purchase totals =	$978.84		$1,054.0707	$1,054.07	$1,054.05	$1,054.10