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	$114.62	4.488%	$119.7641	$119.76	$119.75	$119.80
Purchase #2	$135.87	10.414%	$150.0195	$150.02	$150.00	$150.00
Purchase #3	$20.97	11.145%	$23.3071	$23.31	$23.30	$23.30
Purchase #4	$192.86	4.165%	$200.8926	$200.89	$200.90	$200.90
Purchase #5	$141.33	11.719%	$157.8925	$157.89	$157.90	$157.90
Purchase #6	$93.95	6.442%	$100.0023	$100.00	$100.00	$100.00
Purchase #7	$75.46	13.611%	$85.7309	$85.73	$85.75	$85.70
7 purchase totals =	$775.06		$837.6090	$837.60	$837.60	$837.60