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	$155.62	9.753%	$170.7976	$170.80	$170.80	$170.80
Purchase #2	$42.39	3.380%	$43.8228	$43.82	$43.80	$43.80
Purchase #3	$66.27	7.838%	$71.4642	$71.46	$71.45	$71.50
Purchase #4	$152.50	6.488%	$162.3942	$162.39	$162.40	$162.40
Purchase #5	$166.44	10.275%	$183.5417	$183.54	$183.55	$183.50
Purchase #6	$137.36	8.821%	$149.4765	$149.48	$149.50	$149.50
Purchase #7	$141.49	6.676%	$150.9359	$150.94	$150.95	$150.90
7 purchase totals =	$862.07		$932.4329	$932.43	$932.45	$932.40