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	$179.75	6.725%	$191.8382	$191.84	$191.85	$191.80
Purchase #2	$55.72	5.393%	$58.725	$58.73	$58.75	$58.70
Purchase #3	$31.27	6.660%	$33.3526	$33.35	$33.35	$33.40
Purchase #4	$196.37	13.789%	$223.4475	$223.45	$223.45	$223.40
Purchase #5	$146.61	7.387%	$157.4401	$157.44	$157.45	$157.40
Purchase #6	$143.89	11.687%	$160.7064	$160.71	$160.70	$160.70
Purchase #7	$28.55	10.329%	$31.4989	$31.50	$31.50	$31.50
7 purchase totals =	$782.16		$857.0087	$857.02	$857.05	$856.90