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	$96.76	9.123%	$105.5874	$105.59	$105.60	$105.60
Purchase #2	$59.85	3.868%	$62.165	$62.17	$62.15	$62.20
Purchase #3	$249.32	11.381%	$277.6951	$277.70	$277.70	$277.70
Purchase #4	$105.84	3.825%	$109.8884	$109.89	$109.90	$109.90
Purchase #5	$13.43	5.330%	$14.1458	$14.15	$14.15	$14.10
Purchase #6	$58.25	10.630%	$64.442	$64.44	$64.45	$64.40
Purchase #7	$203.25	6.537%	$216.5365	$216.54	$216.55	$216.50
7 purchase totals =	$786.70		$850.4602	$850.48	$850.50	$850.40