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	$59.94	12.600%	$67.4924	$67.49	$67.50	$67.50
Purchase #2	$49.30	11.335%	$54.8882	$54.89	$54.90	$54.90
Purchase #3	$39.35	13.673%	$44.7303	$44.73	$44.75	$44.70
Purchase #4	$98.98	4.402%	$103.3371	$103.34	$103.35	$103.30
Purchase #5	$8.74	8.117%	$9.4494	$9.45	$9.45	$9.40
Purchase #6	$37.60	11.134%	$41.7864	$41.79	$41.80	$41.80
Purchase #7	$47.75	13.548%	$54.2192	$54.22	$54.20	$54.20
7 purchase totals =	$341.66		$375.9030	$375.91	$375.95	$375.80