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	$156.75	5.291%	$165.0436	$165.04	$165.05	$165.00
Purchase #2	$66.54	4.845%	$69.7639	$69.76	$69.75	$69.80
Purchase #3	$127.32	11.771%	$142.3068	$142.31	$142.30	$142.30
Purchase #4	$40.40	5.119%	$42.4681	$42.47	$42.45	$42.50
Purchase #5	$92.89	13.871%	$105.7748	$105.77	$105.75	$105.80
Purchase #6	$198.94	11.199%	$221.2193	$221.22	$221.20	$221.20
Purchase #7	$57.38	5.818%	$60.7184	$60.72	$60.70	$60.70
7 purchase totals =	$740.22		$807.2949	$807.29	$807.20	$807.30