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	$214.48	3.784%	$222.5959	$222.60	$222.60	$222.60
Purchase #2	$61.46	6.381%	$65.3818	$65.38	$65.40	$65.40
Purchase #3	$250.87	10.421%	$277.0132	$277.01	$277.00	$277.00
Purchase #4	$42.47	11.468%	$47.3405	$47.34	$47.35	$47.30
Purchase #5	$8.93	13.194%	$10.1082	$10.11	$10.10	$10.10
Purchase #6	$245.82	9.588%	$269.3892	$269.39	$269.40	$269.40
Purchase #7	$48.62	10.294%	$53.6249	$53.62	$53.60	$53.60
7 purchase totals =	$872.65		$945.4537	$945.45	$945.45	$945.40