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	$57.59	3.302%	$59.4916	$59.49	$59.50	$59.50
Purchase #2	$235.38	3.537%	$243.7054	$243.71	$243.70	$243.70
Purchase #3	$65.91	8.848%	$71.7417	$71.74	$71.75	$71.70
Purchase #4	$166.91	11.416%	$185.9644	$185.96	$185.95	$186.00
Purchase #5	$175.28	8.430%	$190.0561	$190.06	$190.05	$190.10
Purchase #6	$140.76	9.533%	$154.1787	$154.18	$154.20	$154.20
Purchase #7	$152.90	5.826%	$161.808	$161.81	$161.80	$161.80
7 purchase totals =	$994.73		$1,066.9459	$1,066.95	$1,066.95	$1,067.00