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	$18.82	10.220%	$20.7434	$20.74	$20.75	$20.70
Purchase #2	$38.31	13.536%	$43.4956	$43.50	$43.50	$43.50
Purchase #3	$54.60	13.425%	$61.9301	$61.93	$61.95	$61.90
Purchase #4	$68.78	4.354%	$71.7747	$71.77	$71.75	$71.80
Purchase #5	$136.76	11.426%	$152.3862	$152.39	$152.40	$152.40
Purchase #6	$226.44	11.446%	$252.3583	$252.36	$252.35	$252.40
Purchase #7	$130.89	12.324%	$147.0209	$147.02	$147.00	$147.00
7 purchase totals =	$674.60		$749.7092	$749.71	$749.70	$749.70