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	$130.98	5.621%	$138.3424	$138.34	$138.35	$138.30
Purchase #2	$188.67	4.319%	$196.8187	$196.82	$196.80	$196.80
Purchase #3	$12.37	12.401%	$13.904	$13.90	$13.90	$13.90
Purchase #4	$93.50	12.828%	$105.4942	$105.49	$105.50	$105.50
Purchase #5	$182.44	7.583%	$196.2744	$196.27	$196.25	$196.30
Purchase #6	$154.51	3.316%	$159.6336	$159.63	$159.65	$159.60
Purchase #7	$132.53	7.650%	$142.6685	$142.67	$142.65	$142.70
7 purchase totals =	$895.00		$953.1358	$953.12	$953.10	$953.10