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	$167.37	12.325%	$187.9984	$188.00	$188.00	$188.00
Purchase #2	$190.74	4.467%	$199.2604	$199.26	$199.25	$199.30
Purchase #3	$198.33	10.456%	$219.0674	$219.07	$219.05	$219.10
Purchase #4	$56.83	4.357%	$59.3061	$59.31	$59.30	$59.30
Purchase #5	$169.35	13.529%	$192.2614	$192.26	$192.25	$192.30
Purchase #6	$145.46	4.624%	$152.1861	$152.19	$152.20	$152.20
Purchase #7	$177.55	12.856%	$200.3758	$200.38	$200.40	$200.40
7 purchase totals =	$1,105.63		$1,210.4556	$1,210.47	$1,210.45	$1,210.60