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	$187.69	6.535%	$199.9555	$199.96	$199.95	$200.00
Purchase #2	$158.25	6.301%	$168.2213	$168.22	$168.20	$168.20
Purchase #3	$226.33	11.104%	$251.4617	$251.46	$251.45	$251.50
Purchase #4	$79.60	4.815%	$83.4327	$83.43	$83.45	$83.40
Purchase #5	$50.80	12.794%	$57.2994	$57.30	$57.30	$57.30
Purchase #6	$241.30	5.402%	$254.335	$254.34	$254.35	$254.30
Purchase #7	$11.78	3.383%	$12.1785	$12.18	$12.20	$12.20
7 purchase totals =	$955.75		$1,026.8841	$1,026.89	$1,026.90	$1,026.90