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	$242.80	11.110%	$269.7751	$269.78	$269.80	$269.80
Purchase #2	$80.45	6.434%	$85.6262	$85.63	$85.65	$85.60
Purchase #3	$158.63	8.233%	$171.69	$171.69	$171.70	$171.70
Purchase #4	$207.88	6.582%	$221.5627	$221.56	$221.55	$221.60
Purchase #5	$135.49	12.340%	$152.2095	$152.21	$152.20	$152.20
Purchase #6	$145.61	3.410%	$150.5753	$150.58	$150.60	$150.60
Purchase #7	$37.64	13.171%	$42.5976	$42.60	$42.60	$42.60
7 purchase totals =	$1,008.50		$1,094.0364	$1,094.05	$1,094.10	$1,094.10