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	$191.77	13.227%	$217.1354	$217.14	$217.15	$217.10
Purchase #2	$183.30	3.125%	$189.0281	$189.03	$189.05	$189.00
Purchase #3	$57.44	5.377%	$60.5285	$60.53	$60.55	$60.50
Purchase #4	$71.36	10.106%	$78.5716	$78.57	$78.55	$78.60
Purchase #5	$34.79	10.499%	$38.4426	$38.44	$38.45	$38.40
Purchase #6	$241.88	6.433%	$257.4401	$257.44	$257.45	$257.40
Purchase #7	$90.35	11.676%	$100.8993	$100.90	$100.90	$100.90
7 purchase totals =	$870.89		$942.0456	$942.05	$942.10	$941.90