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	$126.68	10.774%	$140.3285	$140.33	$140.35	$140.30
Purchase #2	$39.58	3.797%	$41.0829	$41.08	$41.10	$41.10
Purchase #3	$32.77	13.468%	$37.1835	$37.18	$37.20	$37.20
Purchase #4	$126.55	13.468%	$143.5938	$143.59	$143.60	$143.60
Purchase #5	$27.49	6.126%	$29.174	$29.17	$29.15	$29.20
Purchase #6	$202.72	10.208%	$223.4137	$223.41	$223.40	$223.40
Purchase #7	$155.31	6.681%	$165.6863	$165.69	$165.70	$165.70
7 purchase totals =	$711.10		$780.4627	$780.45	$780.50	$780.50