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	$163.25	6.513%	$173.8825	$173.88	$173.90	$173.90
Purchase #2	$129.27	5.553%	$136.4484	$136.45	$136.45	$136.40
Purchase #3	$103.41	8.612%	$112.3157	$112.32	$112.30	$112.30
Purchase #4	$217.91	10.196%	$240.1281	$240.13	$240.15	$240.10
Purchase #5	$52.95	8.732%	$57.5736	$57.57	$57.55	$57.60
Purchase #6	$238.61	4.586%	$249.5527	$249.55	$249.55	$249.60
Purchase #7	$85.75	11.400%	$95.5255	$95.53	$95.55	$95.50
7 purchase totals =	$991.15		$1,065.4265	$1,065.43	$1,065.45	$1,065.40