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	$137.67	9.118%	$150.2228	$150.22	$150.20	$150.20
Purchase #2	$31.92	3.372%	$32.9963	$33.00	$33.00	$33.00
Purchase #3	$72.69	7.704%	$78.29	$78.29	$78.30	$78.30
Purchase #4	$193.34	12.638%	$217.7743	$217.77	$217.75	$217.80
Purchase #5	$216.69	6.813%	$231.4531	$231.45	$231.45	$231.50
Purchase #6	$158.92	4.569%	$166.1811	$166.18	$166.20	$166.20
Purchase #7	$173.71	6.544%	$185.0776	$185.08	$185.10	$185.10
7 purchase totals =	$984.94		$1,061.9952	$1,061.99	$1,062.00	$1,062.10