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	$139.60	11.171%	$155.1947	$155.19	$155.20	$155.20
Purchase #2	$100.68	4.647%	$105.3586	$105.36	$105.35	$105.40
Purchase #3	$54.65	4.650%	$57.1912	$57.19	$57.20	$57.20
Purchase #4	$147.47	7.740%	$158.8842	$158.88	$158.90	$158.90
Purchase #5	$61.69	8.561%	$66.9713	$66.97	$66.95	$67.00
Purchase #6	$125.67	3.638%	$130.2419	$130.24	$130.25	$130.20
Purchase #7	$71.72	12.279%	$80.5265	$80.53	$80.55	$80.50
7 purchase totals =	$701.48		$754.3684	$754.36	$754.40	$754.40