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	$200.63	6.843%	$214.3591	$214.36	$214.35	$214.40
Purchase #2	$152.60	12.645%	$171.8963	$171.90	$171.90	$171.90
Purchase #3	$158.89	8.372%	$172.1923	$172.19	$172.20	$172.20
Purchase #4	$232.38	4.801%	$243.5366	$243.54	$243.55	$243.50
Purchase #5	$7.45	4.228%	$7.765	$7.77	$7.75	$7.80
Purchase #6	$228.60	5.348%	$240.8255	$240.83	$240.85	$240.80
Purchase #7	$61.31	13.182%	$69.3919	$69.39	$69.40	$69.40
7 purchase totals =	$1,041.86		$1,119.9667	$1,119.98	$1,120.00	$1,120.00