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	$68.71	6.480%	$73.1624	$73.16	$73.15	$73.20
Purchase #2	$48.41	5.123%	$50.89	$50.89	$50.90	$50.90
Purchase #3	$77.44	7.495%	$83.2441	$83.24	$83.25	$83.20
Purchase #4	$127.84	13.258%	$144.789	$144.79	$144.80	$144.80
Purchase #5	$105.46	4.199%	$109.8883	$109.89	$109.90	$109.90
Purchase #6	$161.67	4.345%	$168.6946	$168.69	$168.70	$168.70
Purchase #7	$150.78	10.268%	$166.2621	$166.26	$166.25	$166.30
7 purchase totals =	$740.31		$796.9305	$796.92	$796.95	$797.00