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	$211.29	11.271%	$235.1045	$235.10	$235.10	$235.10
Purchase #2	$133.33	6.270%	$141.6898	$141.69	$141.70	$141.70
Purchase #3	$198.47	3.653%	$205.7201	$205.72	$205.70	$205.70
Purchase #4	$83.52	8.259%	$90.4179	$90.42	$90.40	$90.40
Purchase #5	$133.46	13.821%	$151.9055	$151.91	$151.90	$151.90
Purchase #6	$73.72	3.514%	$76.3105	$76.31	$76.30	$76.30
Purchase #7	$101.39	9.528%	$111.0504	$111.05	$111.05	$111.10
7 purchase totals =	$935.18		$1,012.1987	$1,012.20	$1,012.15	$1,012.20