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	$125.98	12.598%	$141.851	$141.85	$141.85	$141.90
Purchase #2	$228.62	7.105%	$244.8635	$244.86	$244.85	$244.90
Purchase #3	$165.38	5.201%	$173.9814	$173.98	$174.00	$174.00
Purchase #4	$246.94	6.236%	$262.3392	$262.34	$262.35	$262.30
Purchase #5	$71.32	10.737%	$78.9776	$78.98	$79.00	$79.00
Purchase #6	$53.92	3.499%	$55.8067	$55.81	$55.80	$55.80
Purchase #7	$188.27	11.236%	$209.424	$209.42	$209.40	$209.40
7 purchase totals =	$1,080.43		$1,167.2434	$1,167.24	$1,167.25	$1,167.30