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	$188.99	6.249%	$200.8	$200.80	$200.80	$200.80
Purchase #2	$137.40	11.561%	$153.2848	$153.28	$153.30	$153.30
Purchase #3	$245.40	8.531%	$266.3351	$266.34	$266.35	$266.30
Purchase #4	$179.89	11.115%	$199.8848	$199.88	$199.90	$199.90
Purchase #5	$164.28	8.379%	$178.045	$178.05	$178.05	$178.00
Purchase #6	$108.51	3.782%	$112.6138	$112.61	$112.60	$112.60
Purchase #7	$10.84	13.215%	$12.2725	$12.27	$12.25	$12.30
7 purchase totals =	$1,035.31		$1,123.2360	$1,123.23	$1,123.25	$1,123.20