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	$192.89	10.760%	$213.645	$213.65	$213.65	$213.60
Purchase #2	$170.29	12.703%	$191.9219	$191.92	$191.90	$191.90
Purchase #3	$85.86	11.286%	$95.5502	$95.55	$95.55	$95.60
Purchase #4	$244.79	12.140%	$274.5075	$274.51	$274.50	$274.50
Purchase #5	$206.92	4.532%	$216.2976	$216.30	$216.30	$216.30
Purchase #6	$52.63	4.746%	$55.1278	$55.13	$55.15	$55.10
Purchase #7	$222.34	4.270%	$231.8339	$231.83	$231.85	$231.80
7 purchase totals =	$1,175.72		$1,278.8839	$1,278.89	$1,278.90	$1,278.80