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	$88.83	8.255%	$96.1629	$96.16	$96.15	$96.20
Purchase #2	$224.51	11.171%	$249.59	$249.59	$249.60	$249.60
Purchase #3	$147.56	8.408%	$159.9668	$159.97	$159.95	$160.00
Purchase #4	$128.29	11.154%	$142.5995	$142.60	$142.60	$142.60
Purchase #5	$224.72	10.170%	$247.574	$247.57	$247.55	$247.60
Purchase #6	$36.38	13.397%	$41.2538	$41.25	$41.25	$41.30
Purchase #7	$95.86	10.238%	$105.6741	$105.67	$105.65	$105.70
7 purchase totals =	$946.15		$1,042.8211	$1,042.81	$1,042.75	$1,043.00