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	$144.39	4.561%	$150.9756	$150.98	$151.00	$151.00
Purchase #2	$97.56	4.181%	$101.639	$101.64	$101.65	$101.60
Purchase #3	$149.54	12.431%	$168.1293	$168.13	$168.15	$168.10
Purchase #4	$185.44	12.862%	$209.2913	$209.29	$209.30	$209.30
Purchase #5	$125.94	4.452%	$131.5468	$131.55	$131.55	$131.50
Purchase #6	$37.41	10.448%	$41.3186	$41.32	$41.30	$41.30
Purchase #7	$219.72	9.702%	$241.0372	$241.04	$241.05	$241.00
7 purchase totals =	$960.00		$1,043.9378	$1,043.95	$1,044.00	$1,043.80