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	$90.85	7.434%	$97.6038	$97.60	$97.60	$97.60
Purchase #2	$97.32	9.729%	$106.7883	$106.79	$106.80	$106.80
Purchase #3	$42.63	9.731%	$46.7783	$46.78	$46.80	$46.80
Purchase #4	$198.89	11.489%	$221.7405	$221.74	$221.75	$221.70
Purchase #5	$12.72	13.607%	$14.4508	$14.45	$14.45	$14.50
Purchase #6	$191.61	4.861%	$200.9242	$200.92	$200.90	$200.90
Purchase #7	$195.76	10.651%	$216.6104	$216.61	$216.60	$216.60
7 purchase totals =	$829.78		$904.8963	$904.89	$904.90	$904.90