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	$74.75	12.130%	$83.8172	$83.82	$83.80	$83.80
Purchase #2	$234.28	3.676%	$242.8921	$242.89	$242.90	$242.90
Purchase #3	$40.94	4.643%	$42.8408	$42.84	$42.85	$42.80
Purchase #4	$119.32	4.183%	$124.3112	$124.31	$124.30	$124.30
Purchase #5	$238.52	12.532%	$268.4113	$268.41	$268.40	$268.40
Purchase #6	$153.44	10.232%	$169.14	$169.14	$169.15	$169.10
Purchase #7	$123.43	10.673%	$136.6037	$136.60	$136.60	$136.60
7 purchase totals =	$984.68		$1,068.0163	$1,068.01	$1,068.00	$1,067.90