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	$41.33	10.781%	$45.7858	$45.79	$45.80	$45.80
Purchase #2	$143.67	10.660%	$158.9852	$158.99	$159.00	$159.00
Purchase #3	$21.69	11.386%	$24.1596	$24.16	$24.15	$24.20
Purchase #4	$236.45	3.118%	$243.8225	$243.82	$243.80	$243.80
Purchase #5	$146.82	9.297%	$160.4699	$160.47	$160.45	$160.50
Purchase #6	$211.45	5.270%	$222.5934	$222.59	$222.60	$222.60
Purchase #7	$155.96	13.517%	$177.0411	$177.04	$177.05	$177.00
7 purchase totals =	$957.37		$1,032.8575	$1,032.86	$1,032.85	$1,032.90