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	$90.71	3.717%	$94.0817	$94.08	$94.10	$94.10
Purchase #2	$216.45	10.640%	$239.4803	$239.48	$239.50	$239.50
Purchase #3	$222.32	3.409%	$229.8989	$229.90	$229.90	$229.90
Purchase #4	$225.41	9.536%	$246.9051	$246.91	$246.90	$246.90
Purchase #5	$30.26	8.250%	$32.7565	$32.76	$32.75	$32.80
Purchase #6	$238.30	13.451%	$270.3537	$270.35	$270.35	$270.40
Purchase #7	$64.41	12.506%	$72.4651	$72.47	$72.45	$72.50
7 purchase totals =	$1,087.86		$1,185.9413	$1,185.95	$1,185.95	$1,186.10