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	$131.81	10.453%	$145.5881	$145.59	$145.60	$145.60
Purchase #2	$55.38	10.748%	$61.3322	$61.33	$61.35	$61.30
Purchase #3	$172.37	4.499%	$180.1249	$180.12	$180.10	$180.10
Purchase #4	$12.39	4.165%	$12.906	$12.91	$12.90	$12.90
Purchase #5	$134.90	3.681%	$139.8657	$139.87	$139.85	$139.90
Purchase #6	$159.89	7.814%	$172.3838	$172.38	$172.40	$172.40
Purchase #7	$135.68	3.793%	$140.8263	$140.83	$140.85	$140.80
7 purchase totals =	$802.42		$853.0270	$853.03	$853.05	$853.00