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	$101.82	7.641%	$109.6001	$109.60	$109.60	$109.60
Purchase #2	$136.51	5.341%	$143.801	$143.80	$143.80	$143.80
Purchase #3	$104.83	4.832%	$109.8954	$109.90	$109.90	$109.90
Purchase #4	$73.63	13.477%	$83.5531	$83.55	$83.55	$83.60
Purchase #5	$182.34	9.684%	$199.9978	$200.00	$200.00	$200.00
Purchase #6	$107.56	6.840%	$114.9171	$114.92	$114.90	$114.90
Purchase #7	$229.64	5.136%	$241.4343	$241.43	$241.45	$241.40
7 purchase totals =	$936.33		$1,003.1988	$1,003.20	$1,003.20	$1,003.20