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	$175.27	13.184%	$198.3776	$198.38	$198.40	$198.40
Purchase #2	$165.27	11.752%	$184.6925	$184.69	$184.70	$184.70
Purchase #3	$138.35	10.222%	$152.4921	$152.49	$152.50	$152.50
Purchase #4	$46.85	11.155%	$52.0761	$52.08	$52.10	$52.10
Purchase #5	$38.48	7.335%	$41.3025	$41.30	$41.30	$41.30
Purchase #6	$61.70	9.803%	$67.7485	$67.75	$67.75	$67.70
Purchase #7	$16.46	12.511%	$18.5193	$18.52	$18.50	$18.50
7 purchase totals =	$642.38		$715.2086	$715.21	$715.25	$715.20