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	$232.84	3.602%	$241.2269	$241.23	$241.25	$241.20
Purchase #2	$249.83	10.195%	$275.3002	$275.30	$275.30	$275.30
Purchase #3	$123.44	11.532%	$137.6751	$137.68	$137.70	$137.70
Purchase #4	$213.33	8.648%	$231.7788	$231.78	$231.80	$231.80
Purchase #5	$62.40	4.801%	$65.3958	$65.40	$65.40	$65.40
Purchase #6	$235.61	12.185%	$264.3191	$264.32	$264.30	$264.30
Purchase #7	$225.84	5.443%	$238.1325	$238.13	$238.15	$238.10
7 purchase totals =	$1,343.29		$1,453.8284	$1,453.84	$1,453.90	$1,453.80