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	$48.60	11.629%	$54.2517	$54.25	$54.25	$54.30
Purchase #2	$37.67	6.758%	$40.2157	$40.22	$40.20	$40.20
Purchase #3	$132.48	3.455%	$137.0572	$137.06	$137.05	$137.10
Purchase #4	$182.66	9.585%	$200.168	$200.17	$200.15	$200.20
Purchase #5	$9.79	3.682%	$10.1505	$10.15	$10.15	$10.20
Purchase #6	$63.77	11.751%	$71.2636	$71.26	$71.25	$71.30
Purchase #7	$57.61	3.449%	$59.597	$59.60	$59.60	$59.60
7 purchase totals =	$532.58		$572.7037	$572.71	$572.65	$572.90