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	$91.28	7.606%	$98.2228	$98.22	$98.20	$98.20
Purchase #2	$234.57	10.613%	$259.4649	$259.46	$259.45	$259.50
Purchase #3	$130.31	7.369%	$139.9125	$139.91	$139.90	$139.90
Purchase #4	$146.55	13.624%	$166.516	$166.52	$166.50	$166.50
Purchase #5	$172.80	10.547%	$191.0252	$191.03	$191.05	$191.00
Purchase #6	$173.95	10.633%	$192.4461	$192.45	$192.45	$192.40
Purchase #7	$106.96	11.820%	$119.6027	$119.60	$119.60	$119.60
7 purchase totals =	$1,056.42		$1,167.1902	$1,167.19	$1,167.15	$1,167.10