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	$67.90	3.240%	$70.1	$70.10	$70.10	$70.10
Purchase #2	$50.50	9.421%	$55.2576	$55.26	$55.25	$55.30
Purchase #3	$160.85	7.754%	$173.3223	$173.32	$173.30	$173.30
Purchase #4	$195.62	13.675%	$222.371	$222.37	$222.35	$222.40
Purchase #5	$230.84	12.108%	$258.7901	$258.79	$258.80	$258.80
Purchase #6	$110.89	6.316%	$117.8938	$117.89	$117.90	$117.90
Purchase #7	$189.93	12.485%	$213.6428	$213.64	$213.65	$213.60
7 purchase totals =	$1,006.53		$1,111.3776	$1,111.37	$1,111.35	$1,111.40