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	$171.46	12.272%	$192.5016	$192.50	$192.50	$192.50
Purchase #2	$27.48	3.337%	$28.397	$28.40	$28.40	$28.40
Purchase #3	$150.42	12.579%	$169.3413	$169.34	$169.35	$169.30
Purchase #4	$146.63	12.717%	$165.2769	$165.28	$165.30	$165.30
Purchase #5	$242.39	3.847%	$251.7147	$251.71	$251.70	$251.70
Purchase #6	$172.93	5.723%	$182.8268	$182.83	$182.85	$182.80
Purchase #7	$96.51	7.773%	$104.0117	$104.01	$104.00	$104.00
7 purchase totals =	$1,007.82		$1,094.0700	$1,094.07	$1,094.10	$1,094.00