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	$189.96	3.624%	$196.8442	$196.84	$196.85	$196.80
Purchase #2	$33.59	3.741%	$34.8466	$34.85	$34.85	$34.80
Purchase #3	$200.84	4.701%	$210.2815	$210.28	$210.30	$210.30
Purchase #4	$181.83	13.382%	$206.1625	$206.16	$206.15	$206.20
Purchase #5	$40.55	12.681%	$45.6921	$45.69	$45.70	$45.70
Purchase #6	$17.71	4.284%	$18.4687	$18.47	$18.45	$18.50
Purchase #7	$75.69	11.810%	$84.629	$84.63	$84.65	$84.60
7 purchase totals =	$740.17		$796.9246	$796.92	$796.95	$796.90