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	$144.68	6.121%	$153.5359	$153.54	$153.55	$153.50
Purchase #2	$221.37	3.399%	$228.8944	$228.89	$228.90	$228.90
Purchase #3	$206.71	13.766%	$235.1657	$235.17	$235.15	$235.20
Purchase #4	$236.49	8.575%	$256.769	$256.77	$256.75	$256.80
Purchase #5	$146.33	4.449%	$152.8402	$152.84	$152.85	$152.80
Purchase #6	$6.43	11.456%	$7.1666	$7.17	$7.15	$7.20
Purchase #7	$47.65	7.686%	$51.3124	$51.31	$51.30	$51.30
7 purchase totals =	$1,009.66		$1,085.6842	$1,085.69	$1,085.65	$1,085.70