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	$137.65	12.544%	$154.9168	$154.92	$154.90	$154.90
Purchase #2	$37.81	11.747%	$42.2515	$42.25	$42.25	$42.30
Purchase #3	$71.42	13.488%	$81.0531	$81.05	$81.05	$81.10
Purchase #4	$214.32	10.533%	$236.8943	$236.89	$236.90	$236.90
Purchase #5	$182.31	4.871%	$191.1903	$191.19	$191.20	$191.20
Purchase #6	$233.91	7.276%	$250.9293	$250.93	$250.95	$250.90
Purchase #7	$13.51	9.415%	$14.782	$14.78	$14.80	$14.80
7 purchase totals =	$890.93		$972.0173	$972.01	$972.05	$972.10