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	$54.90	12.788%	$61.9206	$61.92	$61.90	$61.90
Purchase #2	$110.98	7.620%	$119.4367	$119.44	$119.45	$119.40
Purchase #3	$19.31	7.605%	$20.7785	$20.78	$20.80	$20.80
Purchase #4	$221.98	12.616%	$249.985	$249.99	$250.00	$250.00
Purchase #5	$151.71	13.644%	$172.4093	$172.41	$172.40	$172.40
Purchase #6	$137.31	6.364%	$146.0484	$146.05	$146.05	$146.00
Purchase #7	$213.27	7.230%	$228.6894	$228.69	$228.70	$228.70
7 purchase totals =	$909.46		$999.2679	$999.28	$999.30	$999.20