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	$6.38	10.778%	$7.0676	$7.07	$7.05	$7.10
Purchase #2	$142.30	5.761%	$150.4979	$150.50	$150.50	$150.50
Purchase #3	$53.28	12.240%	$59.8015	$59.80	$59.80	$59.80
Purchase #4	$24.55	4.199%	$25.5809	$25.58	$25.60	$25.60
Purchase #5	$54.91	13.569%	$62.3607	$62.36	$62.35	$62.40
Purchase #6	$209.30	13.469%	$237.4906	$237.49	$237.50	$237.50
Purchase #7	$143.82	10.705%	$159.2159	$159.22	$159.20	$159.20
7 purchase totals =	$634.54		$702.0151	$702.02	$702.00	$702.10