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	$187.46	12.103%	$210.1483	$210.15	$210.15	$210.10
Purchase #2	$73.61	7.164%	$78.8834	$78.88	$78.90	$78.90
Purchase #3	$223.73	3.294%	$231.0997	$231.10	$231.10	$231.10
Purchase #4	$61.27	9.218%	$66.9179	$66.92	$66.90	$66.90
Purchase #5	$202.42	3.113%	$208.7213	$208.72	$208.70	$208.70
Purchase #6	$100.90	3.298%	$104.2277	$104.23	$104.25	$104.20
Purchase #7	$183.48	9.419%	$200.762	$200.76	$200.75	$200.80
7 purchase totals =	$1,032.87		$1,100.7603	$1,100.76	$1,100.75	$1,100.70