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	$118.97	13.231%	$134.7109	$134.71	$134.70	$134.70
Purchase #2	$64.53	4.578%	$67.4842	$67.48	$67.50	$67.50
Purchase #3	$188.82	13.260%	$213.8575	$213.86	$213.85	$213.90
Purchase #4	$182.64	7.722%	$196.7435	$196.74	$196.75	$196.70
Purchase #5	$46.26	13.463%	$52.488	$52.49	$52.50	$52.50
Purchase #6	$106.85	12.502%	$120.2084	$120.21	$120.20	$120.20
Purchase #7	$250.90	11.487%	$279.7209	$279.72	$279.70	$279.70
7 purchase totals =	$958.97		$1,065.2134	$1,065.21	$1,065.20	$1,065.20