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	$92.65	9.478%	$101.4314	$101.43	$101.45	$101.40
Purchase #2	$215.68	10.405%	$238.1215	$238.12	$238.10	$238.10
Purchase #3	$232.62	13.277%	$263.505	$263.51	$263.50	$263.50
Purchase #4	$185.41	9.620%	$203.2464	$203.25	$203.25	$203.20
Purchase #5	$82.38	10.191%	$90.7753	$90.78	$90.80	$90.80
Purchase #6	$190.86	4.759%	$199.943	$199.94	$199.95	$199.90
Purchase #7	$31.67	11.416%	$35.2854	$35.29	$35.30	$35.30
7 purchase totals =	$1,031.27		$1,132.3080	$1,132.32	$1,132.35	$1,132.20