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	$98.71	8.361%	$106.9631	$106.96	$106.95	$107.00
Purchase #2	$172.67	13.761%	$196.4311	$196.43	$196.45	$196.40
Purchase #3	$35.55	13.317%	$40.2842	$40.28	$40.30	$40.30
Purchase #4	$59.30	10.199%	$65.348	$65.35	$65.35	$65.30
Purchase #5	$162.75	11.835%	$182.0115	$182.01	$182.00	$182.00
Purchase #6	$181.39	4.289%	$189.1698	$189.17	$189.15	$189.20
Purchase #7	$7.57	4.847%	$7.9369	$7.94	$7.95	$7.90
7 purchase totals =	$717.94		$788.1446	$788.14	$788.15	$788.10