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	$153.77	7.482%	$165.2751	$165.28	$165.30	$165.30
Purchase #2	$181.69	5.385%	$191.474	$191.47	$191.45	$191.50
Purchase #3	$41.78	11.743%	$46.6862	$46.69	$46.70	$46.70
Purchase #4	$17.99	10.830%	$19.9383	$19.94	$19.95	$19.90
Purchase #5	$126.27	4.760%	$132.2805	$132.28	$132.30	$132.30
Purchase #6	$237.86	10.290%	$262.3358	$262.34	$262.35	$262.30
Purchase #7	$41.97	3.691%	$43.5191	$43.52	$43.50	$43.50
7 purchase totals =	$801.33		$861.5090	$861.52	$861.55	$861.50