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	$112.34	5.581%	$118.6097	$118.61	$118.60	$118.60
Purchase #2	$109.69	12.824%	$123.7566	$123.76	$123.75	$123.80
Purchase #3	$211.84	13.356%	$240.1334	$240.13	$240.15	$240.10
Purchase #4	$240.70	4.787%	$252.2223	$252.22	$252.20	$252.20
Purchase #5	$106.76	5.741%	$112.8891	$112.89	$112.90	$112.90
Purchase #6	$56.89	5.478%	$60.0064	$60.01	$60.00	$60.00
Purchase #7	$125.97	12.243%	$141.3925	$141.39	$141.40	$141.40
7 purchase totals =	$964.19		$1,049.0100	$1,049.01	$1,049.00	$1,049.00