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	$47.46	13.745%	$53.9834	$53.98	$54.00	$54.00
Purchase #2	$82.87	4.843%	$86.8834	$86.88	$86.90	$86.90
Purchase #3	$20.45	9.407%	$22.3737	$22.37	$22.35	$22.40
Purchase #4	$21.85	6.347%	$23.2368	$23.24	$23.25	$23.20
Purchase #5	$172.37	6.692%	$183.905	$183.91	$183.90	$183.90
Purchase #6	$69.64	4.119%	$72.5085	$72.51	$72.50	$72.50
Purchase #7	$160.39	4.491%	$167.5931	$167.59	$167.60	$167.60
7 purchase totals =	$575.03		$610.4839	$610.48	$610.50	$610.50