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	$180.48	10.850%	$200.0621	$200.06	$200.05	$200.10
Purchase #2	$127.87	5.370%	$134.7366	$134.74	$134.75	$134.70
Purchase #3	$26.77	10.847%	$29.6737	$29.67	$29.65	$29.70
Purchase #4	$200.34	11.558%	$223.4953	$223.50	$223.50	$223.50
Purchase #5	$29.43	13.158%	$33.3024	$33.30	$33.30	$33.30
Purchase #6	$46.56	4.312%	$48.5677	$48.57	$48.55	$48.60
Purchase #7	$151.48	7.517%	$162.8668	$162.87	$162.85	$162.90
7 purchase totals =	$762.93		$832.7046	$832.71	$832.65	$832.80