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	$156.70	7.738%	$168.8254	$168.83	$168.85	$168.80
Purchase #2	$57.73	11.763%	$64.5208	$64.52	$64.50	$64.50
Purchase #3	$139.36	5.768%	$147.3983	$147.40	$147.40	$147.40
Purchase #4	$236.82	8.278%	$256.424	$256.42	$256.40	$256.40
Purchase #5	$37.78	13.577%	$42.9094	$42.91	$42.90	$42.90
Purchase #6	$99.25	4.762%	$103.9763	$103.98	$104.00	$104.00
Purchase #7	$218.43	13.429%	$247.763	$247.76	$247.75	$247.80
7 purchase totals =	$946.07		$1,031.8172	$1,031.82	$1,031.80	$1,031.80