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	$209.54	10.228%	$230.9718	$230.97	$230.95	$231.00
Purchase #2	$75.62	13.357%	$85.7206	$85.72	$85.70	$85.70
Purchase #3	$56.36	5.507%	$59.4637	$59.46	$59.45	$59.50
Purchase #4	$205.40	8.268%	$222.3825	$222.38	$222.40	$222.40
Purchase #5	$53.34	11.803%	$59.6357	$59.64	$59.65	$59.60
Purchase #6	$237.53	7.777%	$256.0027	$256.00	$256.00	$256.00
Purchase #7	$175.71	5.247%	$184.9295	$184.93	$184.95	$184.90
7 purchase totals =	$1,013.50		$1,099.1065	$1,099.10	$1,099.10	$1,099.10