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	$168.87	13.279%	$191.2942	$191.29	$191.30	$191.30
Purchase #2	$81.39	10.288%	$89.7634	$89.76	$89.75	$89.80
Purchase #3	$43.77	4.831%	$45.8845	$45.88	$45.90	$45.90
Purchase #4	$44.48	7.706%	$47.9076	$47.91	$47.90	$47.90
Purchase #5	$222.83	12.799%	$251.35	$251.35	$251.35	$251.40
Purchase #6	$226.99	11.109%	$252.2063	$252.21	$252.20	$252.20
Purchase #7	$58.57	11.652%	$65.3946	$65.39	$65.40	$65.40
7 purchase totals =	$846.90		$943.8006	$943.79	$943.80	$943.90