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	$241.53	7.809%	$260.3911	$260.39	$260.40	$260.40
Purchase #2	$90.56	13.620%	$102.8943	$102.89	$102.90	$102.90
Purchase #3	$166.86	3.437%	$172.595	$172.60	$172.60	$172.60
Purchase #4	$190.29	11.721%	$212.5939	$212.59	$212.60	$212.60
Purchase #5	$215.79	7.512%	$232.0001	$232.00	$232.00	$232.00
Purchase #6	$101.70	9.586%	$111.449	$111.45	$111.45	$111.40
Purchase #7	$135.83	6.777%	$145.0352	$145.04	$145.05	$145.00
7 purchase totals =	$1,142.56		$1,236.9586	$1,236.96	$1,237.00	$1,236.90