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	$135.31	12.196%	$151.8124	$151.81	$151.80	$151.80
Purchase #2	$92.90	11.403%	$103.4934	$103.49	$103.50	$103.50
Purchase #3	$141.79	11.434%	$158.0023	$158.00	$158.00	$158.00
Purchase #4	$13.50	9.247%	$14.7483	$14.75	$14.75	$14.70
Purchase #5	$107.41	7.386%	$115.3433	$115.34	$115.35	$115.30
Purchase #6	$172.57	13.618%	$196.0706	$196.07	$196.05	$196.10
Purchase #7	$42.41	9.696%	$46.5221	$46.52	$46.50	$46.50
7 purchase totals =	$705.89		$785.9924	$785.98	$785.95	$785.90