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	$39.82	4.798%	$41.7306	$41.73	$41.75	$41.70
Purchase #2	$123.91	8.591%	$134.5551	$134.56	$134.55	$134.60
Purchase #3	$121.89	12.297%	$136.8788	$136.88	$136.90	$136.90
Purchase #4	$92.64	8.246%	$100.2791	$100.28	$100.30	$100.30
Purchase #5	$61.53	11.454%	$68.5776	$68.58	$68.60	$68.60
Purchase #6	$63.26	11.274%	$70.3919	$70.39	$70.40	$70.40
Purchase #7	$157.57	9.692%	$172.8417	$172.84	$172.85	$172.80
7 purchase totals =	$660.62		$725.2548	$725.26	$725.35	$725.30