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	$36.31	3.453%	$37.5638	$37.56	$37.55	$37.60
Purchase #2	$131.55	6.857%	$140.5704	$140.57	$140.55	$140.60
Purchase #3	$90.77	4.232%	$94.6114	$94.61	$94.60	$94.60
Purchase #4	$219.92	7.542%	$236.5064	$236.51	$236.50	$236.50
Purchase #5	$48.90	11.306%	$54.4286	$54.43	$54.45	$54.40
Purchase #6	$31.84	13.127%	$36.0196	$36.02	$36.00	$36.00
Purchase #7	$183.85	7.120%	$196.9401	$196.94	$196.95	$196.90
7 purchase totals =	$743.14		$796.6403	$796.64	$796.60	$796.60