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	$112.59	10.129%	$123.9942	$123.99	$124.00	$124.00
Purchase #2	$45.62	9.112%	$49.7769	$49.78	$49.80	$49.80
Purchase #3	$180.54	8.682%	$196.2145	$196.21	$196.20	$196.20
Purchase #4	$197.34	12.577%	$222.1595	$222.16	$222.15	$222.20
Purchase #5	$215.63	4.613%	$225.577	$225.58	$225.60	$225.60
Purchase #6	$83.41	4.316%	$87.01	$87.01	$87.00	$87.00
Purchase #7	$212.42	4.775%	$222.5631	$222.56	$222.55	$222.60
7 purchase totals =	$1,047.55		$1,127.2952	$1,127.29	$1,127.30	$1,127.40