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	$203.45	3.372%	$210.3103	$210.31	$210.30	$210.30
Purchase #2	$99.73	3.524%	$103.2445	$103.24	$103.25	$103.20
Purchase #3	$163.81	5.379%	$172.6213	$172.62	$172.60	$172.60
Purchase #4	$201.44	7.867%	$217.2873	$217.29	$217.30	$217.30
Purchase #5	$93.93	6.417%	$99.9575	$99.96	$99.95	$100.00
Purchase #6	$169.93	5.677%	$179.5769	$179.58	$179.60	$179.60
Purchase #7	$113.48	13.306%	$128.5796	$128.58	$128.60	$128.60
7 purchase totals =	$1,045.77		$1,111.5774	$1,111.58	$1,111.60	$1,111.60