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	$93.25	11.102%	$103.6026	$103.60	$103.60	$103.60
Purchase #2	$168.72	6.784%	$180.166	$180.17	$180.15	$180.20
Purchase #3	$35.99	3.460%	$37.2353	$37.24	$37.25	$37.20
Purchase #4	$238.79	7.368%	$256.384	$256.38	$256.40	$256.40
Purchase #5	$37.60	13.249%	$42.5816	$42.58	$42.60	$42.60
Purchase #6	$248.71	6.694%	$265.3586	$265.36	$265.35	$265.40
Purchase #7	$41.53	10.407%	$45.852	$45.85	$45.85	$45.90
7 purchase totals =	$864.59		$931.1801	$931.18	$931.20	$931.30