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	$231.62	4.869%	$242.8976	$242.90	$242.90	$242.90
Purchase #2	$5.35	10.574%	$5.9157	$5.92	$5.90	$5.90
Purchase #3	$62.52	8.161%	$67.6223	$67.62	$67.60	$67.60
Purchase #4	$37.57	7.497%	$40.3866	$40.39	$40.40	$40.40
Purchase #5	$103.42	4.818%	$108.4028	$108.40	$108.40	$108.40
Purchase #6	$99.43	5.356%	$104.7555	$104.76	$104.75	$104.80
Purchase #7	$126.66	8.788%	$137.7909	$137.79	$137.80	$137.80
7 purchase totals =	$666.57		$707.7714	$707.78	$707.75	$707.80