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	$65.27	8.593%	$70.8787	$70.88	$70.90	$70.90
Purchase #2	$103.57	8.462%	$112.3341	$112.33	$112.35	$112.30
Purchase #3	$232.38	5.103%	$244.2384	$244.24	$244.25	$244.20
Purchase #4	$148.80	6.507%	$158.4824	$158.48	$158.50	$158.50
Purchase #5	$43.77	4.674%	$45.8158	$45.82	$45.80	$45.80
Purchase #6	$90.75	13.761%	$103.2381	$103.24	$103.25	$103.20
Purchase #7	$241.90	9.321%	$264.4475	$264.45	$264.45	$264.40
7 purchase totals =	$926.44		$999.4350	$999.44	$999.50	$999.30