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	$224.41	6.401%	$238.7745	$238.77	$238.75	$238.80
Purchase #2	$210.50	11.750%	$235.2338	$235.23	$235.25	$235.20
Purchase #3	$22.79	9.285%	$24.9061	$24.91	$24.90	$24.90
Purchase #4	$172.64	7.440%	$185.4844	$185.48	$185.50	$185.50
Purchase #5	$42.48	6.573%	$45.2722	$45.27	$45.25	$45.30
Purchase #6	$226.54	7.243%	$242.9483	$242.95	$242.95	$242.90
Purchase #7	$116.40	10.373%	$128.4742	$128.47	$128.45	$128.50
7 purchase totals =	$1,015.76		$1,101.0935	$1,101.08	$1,101.05	$1,101.10