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	$39.26	5.811%	$41.5414	$41.54	$41.55	$41.50
Purchase #2	$157.49	4.845%	$165.1204	$165.12	$165.10	$165.10
Purchase #3	$190.28	8.250%	$205.9781	$205.98	$206.00	$206.00
Purchase #4	$47.54	10.453%	$52.5094	$52.51	$52.50	$52.50
Purchase #5	$74.41	4.873%	$78.036	$78.04	$78.05	$78.00
Purchase #6	$127.34	7.178%	$136.4805	$136.48	$136.50	$136.50
Purchase #7	$135.86	3.368%	$140.4358	$140.44	$140.45	$140.40
7 purchase totals =	$772.18		$820.1016	$820.11	$820.15	$820.00