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	$52.40	12.625%	$59.0155	$59.02	$59.00	$59.00
Purchase #2	$223.63	9.301%	$244.4298	$244.43	$244.45	$244.40
Purchase #3	$44.35	4.288%	$46.2517	$46.25	$46.25	$46.30
Purchase #4	$56.71	9.394%	$62.0373	$62.04	$62.05	$62.00
Purchase #5	$182.72	13.873%	$208.0687	$208.07	$208.05	$208.10
Purchase #6	$204.40	3.728%	$212.02	$212.02	$212.00	$212.00
Purchase #7	$50.52	9.685%	$55.4129	$55.41	$55.40	$55.40
7 purchase totals =	$814.73		$887.2359	$887.24	$887.20	$887.20