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	$218.84	6.835%	$233.7977	$233.80	$233.80	$233.80
Purchase #2	$81.46	11.618%	$90.924	$90.92	$90.90	$90.90
Purchase #3	$37.63	11.105%	$41.8088	$41.81	$41.80	$41.80
Purchase #4	$233.34	13.717%	$265.3472	$265.35	$265.35	$265.30
Purchase #5	$206.34	8.817%	$224.533	$224.53	$224.55	$224.50
Purchase #6	$100.50	5.379%	$105.9059	$105.91	$105.90	$105.90
Purchase #7	$219.56	11.822%	$245.5164	$245.52	$245.50	$245.50
7 purchase totals =	$1,097.67		$1,207.8330	$1,207.84	$1,207.80	$1,207.70