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	$189.66	5.698%	$200.4668	$200.47	$200.45	$200.50
Purchase #2	$26.99	13.429%	$30.6145	$30.61	$30.60	$30.60
Purchase #3	$95.89	6.154%	$101.7911	$101.79	$101.80	$101.80
Purchase #4	$179.79	11.538%	$200.5342	$200.53	$200.55	$200.50
Purchase #5	$146.43	3.372%	$151.3676	$151.37	$151.35	$151.40
Purchase #6	$80.89	3.256%	$83.5238	$83.52	$83.50	$83.50
Purchase #7	$191.81	13.855%	$218.3853	$218.39	$218.40	$218.40
7 purchase totals =	$911.46		$986.6833	$986.68	$986.65	$986.70