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	$92.85	11.413%	$103.447	$103.45	$103.45	$103.40
Purchase #2	$77.30	6.281%	$82.1552	$82.16	$82.15	$82.20
Purchase #3	$238.92	5.119%	$251.1503	$251.15	$251.15	$251.20
Purchase #4	$187.58	5.638%	$198.1558	$198.16	$198.15	$198.20
Purchase #5	$200.43	9.171%	$218.8114	$218.81	$218.80	$218.80
Purchase #6	$98.74	8.676%	$107.3067	$107.31	$107.30	$107.30
Purchase #7	$165.61	3.515%	$171.4312	$171.43	$171.45	$171.40
7 purchase totals =	$1,061.43		$1,132.4576	$1,132.47	$1,132.45	$1,132.50