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	$201.83	3.495%	$208.884	$208.88	$208.90	$208.90
Purchase #2	$83.76	9.329%	$91.574	$91.57	$91.55	$91.60
Purchase #3	$136.63	8.702%	$148.5195	$148.52	$148.50	$148.50
Purchase #4	$85.55	10.189%	$94.2667	$94.27	$94.25	$94.30
Purchase #5	$95.79	12.779%	$108.031	$108.03	$108.05	$108.00
Purchase #6	$94.63	11.109%	$105.1424	$105.14	$105.15	$105.10
Purchase #7	$153.67	9.657%	$168.5099	$168.51	$168.50	$168.50
7 purchase totals =	$851.86		$924.9275	$924.92	$924.90	$924.90