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	$172.42	10.327%	$190.2258	$190.23	$190.25	$190.20
Purchase #2	$131.49	8.770%	$143.0217	$143.02	$143.00	$143.00
Purchase #3	$53.44	10.843%	$59.2345	$59.23	$59.25	$59.20
Purchase #4	$239.48	13.447%	$271.6829	$271.68	$271.70	$271.70
Purchase #5	$99.77	11.311%	$111.055	$111.06	$111.05	$111.10
Purchase #6	$123.56	10.672%	$136.7463	$136.75	$136.75	$136.70
Purchase #7	$177.43	6.404%	$188.7926	$188.79	$188.80	$188.80
7 purchase totals =	$997.59		$1,100.7588	$1,100.76	$1,100.80	$1,100.70