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	$184.48	8.165%	$199.5428	$199.54	$199.55	$199.50
Purchase #2	$239.88	13.300%	$271.784	$271.78	$271.80	$271.80
Purchase #3	$194.78	11.837%	$217.8361	$217.84	$217.85	$217.80
Purchase #4	$91.44	3.392%	$94.5416	$94.54	$94.55	$94.50
Purchase #5	$31.43	8.449%	$34.0855	$34.09	$34.10	$34.10
Purchase #6	$41.60	8.248%	$45.0312	$45.03	$45.05	$45.00
Purchase #7	$250.34	5.671%	$264.5368	$264.54	$264.55	$264.50
7 purchase totals =	$1,033.95		$1,127.3580	$1,127.36	$1,127.45	$1,127.20