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	$31.34	4.124%	$32.6325	$32.63	$32.65	$32.60
Purchase #2	$166.59	3.314%	$172.1108	$172.11	$172.10	$172.10
Purchase #3	$146.82	11.727%	$164.0376	$164.04	$164.05	$164.00
Purchase #4	$214.56	11.601%	$239.4511	$239.45	$239.45	$239.50
Purchase #5	$231.47	5.122%	$243.3259	$243.33	$243.35	$243.30
Purchase #6	$20.54	8.470%	$22.2797	$22.28	$22.30	$22.30
Purchase #7	$177.39	4.761%	$185.8355	$185.84	$185.85	$185.80
7 purchase totals =	$988.71		$1,059.6731	$1,059.68	$1,059.75	$1,059.60