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	$124.88	6.628%	$133.157	$133.16	$133.15	$133.20
Purchase #2	$123.80	12.462%	$139.228	$139.23	$139.25	$139.20
Purchase #3	$247.49	8.865%	$269.43	$269.43	$269.45	$269.40
Purchase #4	$225.26	13.308%	$255.2376	$255.24	$255.25	$255.20
Purchase #5	$71.71	8.726%	$77.9674	$77.97	$77.95	$78.00
Purchase #6	$82.90	6.350%	$88.1642	$88.16	$88.15	$88.20
Purchase #7	$234.74	9.218%	$256.3783	$256.38	$256.40	$256.40
7 purchase totals =	$1,110.78		$1,219.5625	$1,219.57	$1,219.60	$1,219.60