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	$66.33	10.311%	$73.1693	$73.17	$73.15	$73.20
Purchase #2	$197.76	10.665%	$218.8511	$218.85	$218.85	$218.90
Purchase #3	$242.70	4.510%	$253.6458	$253.65	$253.65	$253.60
Purchase #4	$81.96	10.860%	$90.8609	$90.86	$90.85	$90.90
Purchase #5	$219.64	5.395%	$231.4896	$231.49	$231.50	$231.50
Purchase #6	$47.31	6.362%	$50.3199	$50.32	$50.30	$50.30
Purchase #7	$205.98	6.329%	$219.0165	$219.02	$219.00	$219.00
7 purchase totals =	$1,061.68		$1,137.3531	$1,137.36	$1,137.30	$1,137.40