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	$93.42	7.620%	$100.5386	$100.54	$100.55	$100.50
Purchase #2	$42.43	7.340%	$45.5444	$45.54	$45.55	$45.50
Purchase #3	$108.31	3.656%	$112.2698	$112.27	$112.25	$112.30
Purchase #4	$69.53	11.690%	$77.6581	$77.66	$77.65	$77.70
Purchase #5	$56.71	9.448%	$62.068	$62.07	$62.05	$62.10
Purchase #6	$93.86	5.794%	$99.2982	$99.30	$99.30	$99.30
Purchase #7	$35.64	7.678%	$38.3764	$38.38	$38.40	$38.40
7 purchase totals =	$499.90		$535.7535	$535.76	$535.75	$535.80