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	$192.45	12.289%	$216.1002	$216.10	$216.10	$216.10
Purchase #2	$236.66	3.721%	$245.4661	$245.47	$245.45	$245.50
Purchase #3	$107.55	3.772%	$111.6068	$111.61	$111.60	$111.60
Purchase #4	$122.80	10.180%	$135.301	$135.30	$135.30	$135.30
Purchase #5	$152.38	8.617%	$165.5106	$165.51	$165.50	$165.50
Purchase #6	$50.38	7.637%	$54.2275	$54.23	$54.25	$54.20
Purchase #7	$145.32	7.168%	$155.7365	$155.74	$155.75	$155.70
7 purchase totals =	$1,007.54		$1,083.9487	$1,083.96	$1,083.95	$1,083.90