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	$53.80	11.281%	$59.8692	$59.87	$59.85	$59.90
Purchase #2	$106.54	5.734%	$112.649	$112.65	$112.65	$112.60
Purchase #3	$161.33	4.779%	$169.04	$169.04	$169.05	$169.00
Purchase #4	$224.94	13.438%	$255.1674	$255.17	$255.15	$255.20
Purchase #5	$21.94	3.347%	$22.6743	$22.67	$22.65	$22.70
Purchase #6	$107.70	8.473%	$116.8254	$116.83	$116.85	$116.80
Purchase #7	$40.31	12.456%	$45.331	$45.33	$45.35	$45.30
7 purchase totals =	$716.56		$781.5563	$781.56	$781.55	$781.50