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	$171.88	10.821%	$190.4791	$190.48	$190.50	$190.50
Purchase #2	$27.27	4.801%	$28.5792	$28.58	$28.60	$28.60
Purchase #3	$198.77	13.255%	$225.117	$225.12	$225.10	$225.10
Purchase #4	$185.78	13.272%	$210.4367	$210.44	$210.45	$210.40
Purchase #5	$226.52	6.498%	$241.2393	$241.24	$241.25	$241.20
Purchase #6	$145.34	8.187%	$157.239	$157.24	$157.25	$157.20
Purchase #7	$133.53	7.381%	$143.3858	$143.39	$143.40	$143.40
7 purchase totals =	$1,089.09		$1,196.4761	$1,196.49	$1,196.55	$1,196.40