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	$104.28	11.648%	$116.4265	$116.43	$116.45	$116.40
Purchase #2	$40.47	5.290%	$42.6109	$42.61	$42.60	$42.60
Purchase #3	$161.56	13.194%	$182.8762	$182.88	$182.90	$182.90
Purchase #4	$235.74	7.536%	$253.5054	$253.51	$253.50	$253.50
Purchase #5	$13.53	12.407%	$15.2087	$15.21	$15.20	$15.20
Purchase #6	$168.52	8.872%	$183.4711	$183.47	$183.45	$183.50
Purchase #7	$238.29	8.834%	$259.3405	$259.34	$259.35	$259.30
7 purchase totals =	$962.39		$1,053.4393	$1,053.45	$1,053.45	$1,053.40