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	$104.66	7.208%	$112.2039	$112.20	$112.20	$112.20
Purchase #2	$172.65	3.775%	$179.1675	$179.17	$179.15	$179.20
Purchase #3	$19.44	11.165%	$21.6105	$21.61	$21.60	$21.60
Purchase #4	$92.85	3.488%	$96.0886	$96.09	$96.10	$96.10
Purchase #5	$155.30	6.831%	$165.9085	$165.91	$165.90	$165.90
Purchase #6	$105.86	3.797%	$109.8795	$109.88	$109.90	$109.90
Purchase #7	$202.89	5.153%	$213.3449	$213.34	$213.35	$213.30
7 purchase totals =	$853.65		$898.2034	$898.20	$898.20	$898.20