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	$132.28	11.468%	$147.4499	$147.45	$147.45	$147.40
Purchase #2	$52.39	6.275%	$55.6775	$55.68	$55.70	$55.70
Purchase #3	$222.44	12.493%	$250.2294	$250.23	$250.25	$250.20
Purchase #4	$6.71	11.170%	$7.4595	$7.46	$7.45	$7.50
Purchase #5	$109.43	7.410%	$117.5388	$117.54	$117.55	$117.50
Purchase #6	$246.76	6.372%	$262.4835	$262.48	$262.50	$262.50
Purchase #7	$202.27	10.695%	$223.9028	$223.90	$223.90	$223.90
7 purchase totals =	$972.28		$1,064.7414	$1,064.74	$1,064.80	$1,064.70