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	$160.34	12.452%	$180.3055	$180.31	$180.30	$180.30
Purchase #2	$214.95	4.691%	$225.0333	$225.03	$225.05	$225.00
Purchase #3	$83.47	6.797%	$89.1435	$89.14	$89.15	$89.10
Purchase #4	$144.84	4.624%	$151.5374	$151.54	$151.55	$151.50
Purchase #5	$215.78	7.184%	$231.2816	$231.28	$231.30	$231.30
Purchase #6	$178.94	4.815%	$187.556	$187.56	$187.55	$187.60
Purchase #7	$89.43	8.341%	$96.8894	$96.89	$96.90	$96.90
7 purchase totals =	$1,087.75		$1,161.7467	$1,161.75	$1,161.80	$1,161.70