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	$106.30	10.204%	$117.1469	$117.15	$117.15	$117.10
Purchase #2	$29.52	10.216%	$32.5358	$32.54	$32.55	$32.50
Purchase #3	$212.27	4.789%	$222.4356	$222.44	$222.45	$222.40
Purchase #4	$183.80	6.589%	$195.9106	$195.91	$195.90	$195.90
Purchase #5	$91.53	11.773%	$102.3058	$102.31	$102.30	$102.30
Purchase #6	$33.56	12.603%	$37.7896	$37.79	$37.80	$37.80
Purchase #7	$10.72	4.474%	$11.1996	$11.20	$11.20	$11.20
7 purchase totals =	$667.70		$719.3239	$719.34	$719.35	$719.20