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	$245.27	8.296%	$265.6176	$265.62	$265.60	$265.60
Purchase #2	$73.29	8.458%	$79.4889	$79.49	$79.50	$79.50
Purchase #3	$172.82	13.443%	$196.0522	$196.05	$196.05	$196.10
Purchase #4	$53.78	9.504%	$58.8913	$58.89	$58.90	$58.90
Purchase #5	$161.34	7.799%	$173.9229	$173.92	$173.90	$173.90
Purchase #6	$160.48	5.802%	$169.791	$169.79	$169.80	$169.80
Purchase #7	$28.36	9.631%	$31.0914	$31.09	$31.10	$31.10
7 purchase totals =	$895.34		$974.8553	$974.85	$974.85	$974.90