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	$134.97	9.107%	$147.2617	$147.26	$147.25	$147.30
Purchase #2	$198.59	6.767%	$212.0286	$212.03	$212.05	$212.00
Purchase #3	$77.32	8.196%	$83.6571	$83.66	$83.65	$83.70
Purchase #4	$250.84	7.857%	$270.5485	$270.55	$270.55	$270.50
Purchase #5	$88.72	13.589%	$100.7762	$100.78	$100.80	$100.80
Purchase #6	$137.37	4.769%	$143.9212	$143.92	$143.90	$143.90
Purchase #7	$146.98	12.442%	$165.2673	$165.27	$165.25	$165.30
7 purchase totals =	$1,034.79		$1,123.4606	$1,123.47	$1,123.45	$1,123.50