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	$43.33	5.497%	$45.7119	$45.71	$45.70	$45.70
Purchase #2	$21.75	5.422%	$22.9293	$22.93	$22.95	$22.90
Purchase #3	$157.64	13.494%	$178.9119	$178.91	$178.90	$178.90
Purchase #4	$79.82	7.197%	$85.5646	$85.56	$85.55	$85.60
Purchase #5	$75.25	10.364%	$83.0489	$83.05	$83.05	$83.00
Purchase #6	$55.87	9.280%	$61.0547	$61.05	$61.05	$61.10
Purchase #7	$135.91	5.493%	$143.3755	$143.38	$143.40	$143.40
7 purchase totals =	$569.57		$620.5968	$620.59	$620.60	$620.60