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	$142.50	13.175%	$161.2744	$161.27	$161.25	$161.30
Purchase #2	$51.73	5.536%	$54.5938	$54.59	$54.60	$54.60
Purchase #3	$67.56	11.485%	$75.3193	$75.32	$75.30	$75.30
Purchase #4	$237.64	12.429%	$267.1763	$267.18	$267.20	$267.20
Purchase #5	$215.25	9.601%	$235.9162	$235.92	$235.90	$235.90
Purchase #6	$125.76	4.558%	$131.4921	$131.49	$131.50	$131.50
Purchase #7	$233.89	9.837%	$256.8978	$256.90	$256.90	$256.90
7 purchase totals =	$1,074.33		$1,182.6699	$1,182.67	$1,182.65	$1,182.70