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	$131.54	11.527%	$146.7026	$146.70	$146.70	$146.70
Purchase #2	$101.84	3.447%	$105.3504	$105.35	$105.35	$105.40
Purchase #3	$76.98	12.225%	$86.3908	$86.39	$86.40	$86.40
Purchase #4	$145.90	13.243%	$165.2215	$165.22	$165.20	$165.20
Purchase #5	$188.38	12.245%	$211.4471	$211.45	$211.45	$211.40
Purchase #6	$125.50	9.104%	$136.9255	$136.93	$136.95	$136.90
Purchase #7	$243.75	12.803%	$274.9573	$274.96	$274.95	$275.00
7 purchase totals =	$1,013.89		$1,126.9952	$1,127.00	$1,127.00	$1,127.00