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	$118.40	8.543%	$128.5149	$128.51	$128.50	$128.50
Purchase #2	$198.37	12.871%	$223.9022	$223.90	$223.90	$223.90
Purchase #3	$161.68	3.245%	$166.9265	$166.93	$166.95	$166.90
Purchase #4	$92.51	13.831%	$105.3051	$105.31	$105.30	$105.30
Purchase #5	$229.95	7.360%	$246.8743	$246.87	$246.85	$246.90
Purchase #6	$152.40	4.285%	$158.9303	$158.93	$158.95	$158.90
Purchase #7	$17.29	12.275%	$19.4123	$19.41	$19.40	$19.40
7 purchase totals =	$970.60		$1,049.8656	$1,049.86	$1,049.85	$1,049.80