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	$247.51	10.767%	$274.1594	$274.16	$274.15	$274.20
Purchase #2	$67.83	6.774%	$72.4248	$72.42	$72.40	$72.40
Purchase #3	$93.60	7.550%	$100.6668	$100.67	$100.65	$100.70
Purchase #4	$136.79	6.570%	$145.7771	$145.78	$145.80	$145.80
Purchase #5	$220.28	7.203%	$236.1468	$236.15	$236.15	$236.10
Purchase #6	$104.71	12.103%	$117.3831	$117.38	$117.40	$117.40
Purchase #7	$96.93	11.288%	$107.8715	$107.87	$107.85	$107.90
7 purchase totals =	$967.65		$1,054.4295	$1,054.43	$1,054.40	$1,054.50