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	$73.98	11.425%	$82.4322	$82.43	$82.45	$82.40
Purchase #2	$124.47	7.783%	$134.1575	$134.16	$134.15	$134.20
Purchase #3	$199.53	12.794%	$225.0579	$225.06	$225.05	$225.10
Purchase #4	$54.97	12.492%	$61.8369	$61.84	$61.85	$61.80
Purchase #5	$222.67	9.306%	$243.3917	$243.39	$243.40	$243.40
Purchase #6	$160.78	7.383%	$172.6504	$172.65	$172.65	$172.70
Purchase #7	$128.72	5.726%	$136.0905	$136.09	$136.10	$136.10
7 purchase totals =	$965.12		$1,055.6171	$1,055.62	$1,055.65	$1,055.70