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	$76.60	11.159%	$85.1478	$85.15	$85.15	$85.10
Purchase #2	$210.29	8.831%	$228.8607	$228.86	$228.85	$228.90
Purchase #3	$194.61	8.366%	$210.8911	$210.89	$210.90	$210.90
Purchase #4	$161.31	4.566%	$168.6754	$168.68	$168.70	$168.70
Purchase #5	$123.53	13.165%	$139.7927	$139.79	$139.80	$139.80
Purchase #6	$66.71	7.381%	$71.6339	$71.63	$71.65	$71.60
Purchase #7	$50.46	11.381%	$56.2029	$56.20	$56.20	$56.20
7 purchase totals =	$883.51		$961.2045	$961.20	$961.25	$961.20