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	$131.80	12.494%	$148.2671	$148.27	$148.25	$148.30
Purchase #2	$10.33	11.712%	$11.5398	$11.54	$11.55	$11.50
Purchase #3	$52.58	4.453%	$54.9214	$54.92	$54.90	$54.90
Purchase #4	$24.95	13.503%	$28.319	$28.32	$28.30	$28.30
Purchase #5	$69.92	12.451%	$78.6257	$78.63	$78.65	$78.60
Purchase #6	$27.69	12.750%	$31.2205	$31.22	$31.20	$31.20
Purchase #7	$206.98	7.861%	$223.2507	$223.25	$223.25	$223.30
7 purchase totals =	$524.25		$576.1442	$576.15	$576.10	$576.10