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	$126.82	3.425%	$131.1636	$131.16	$131.15	$131.20
Purchase #2	$83.35	4.179%	$86.8332	$86.83	$86.85	$86.80
Purchase #3	$105.99	4.869%	$111.1507	$111.15	$111.15	$111.20
Purchase #4	$140.31	11.475%	$156.4106	$156.41	$156.40	$156.40
Purchase #5	$127.87	5.830%	$135.3248	$135.32	$135.30	$135.30
Purchase #6	$250.93	5.351%	$264.3573	$264.36	$264.35	$264.40
Purchase #7	$59.34	12.460%	$66.7338	$66.73	$66.75	$66.70
7 purchase totals =	$894.61		$951.9740	$951.96	$951.95	$952.00