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	$174.69	12.489%	$196.507	$196.51	$196.50	$196.50
Purchase #2	$178.51	10.646%	$197.5142	$197.51	$197.50	$197.50
Purchase #3	$154.52	13.791%	$175.8299	$175.83	$175.85	$175.80
Purchase #4	$243.73	5.146%	$256.2723	$256.27	$256.25	$256.30
Purchase #5	$42.67	10.729%	$47.2481	$47.25	$47.25	$47.20
Purchase #6	$226.54	4.642%	$237.056	$237.06	$237.05	$237.10
Purchase #7	$234.50	11.451%	$261.3526	$261.35	$261.35	$261.40
7 purchase totals =	$1,255.16		$1,371.7801	$1,371.78	$1,371.75	$1,371.80