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	$64.47	10.749%	$71.3999	$71.40	$71.40	$71.40
Purchase #2	$126.68	12.540%	$142.5657	$142.57	$142.55	$142.60
Purchase #3	$95.27	3.510%	$98.614	$98.61	$98.60	$98.60
Purchase #4	$39.54	8.370%	$42.8495	$42.85	$42.85	$42.80
Purchase #5	$96.37	9.775%	$105.7902	$105.79	$105.80	$105.80
Purchase #6	$15.80	3.605%	$16.3696	$16.37	$16.35	$16.40
Purchase #7	$172.79	13.145%	$195.5032	$195.50	$195.50	$195.50
7 purchase totals =	$610.92		$673.0921	$673.09	$673.05	$673.10