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	$91.74	13.225%	$103.8726	$103.87	$103.85	$103.90
Purchase #2	$200.62	10.871%	$222.4294	$222.43	$222.45	$222.40
Purchase #3	$46.59	11.611%	$51.9996	$52.00	$52.00	$52.00
Purchase #4	$141.77	12.378%	$159.3183	$159.32	$159.30	$159.30
Purchase #5	$206.59	12.261%	$231.92	$231.92	$231.90	$231.90
Purchase #6	$105.55	12.864%	$119.128	$119.13	$119.15	$119.10
Purchase #7	$250.99	8.629%	$272.6479	$272.65	$272.65	$272.60
7 purchase totals =	$1,043.85		$1,161.3158	$1,161.32	$1,161.30	$1,161.20