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	$59.35	13.738%	$67.5035	$67.50	$67.50	$67.50
Purchase #2	$75.94	12.350%	$85.3186	$85.32	$85.30	$85.30
Purchase #3	$169.56	4.747%	$177.609	$177.61	$177.60	$177.60
Purchase #4	$215.89	4.150%	$224.8494	$224.85	$224.85	$224.80
Purchase #5	$239.37	3.857%	$248.6025	$248.60	$248.60	$248.60
Purchase #6	$171.54	9.512%	$187.8569	$187.86	$187.85	$187.90
Purchase #7	$192.56	8.226%	$208.4	$208.40	$208.40	$208.40
7 purchase totals =	$1,124.21		$1,200.1399	$1,200.14	$1,200.10	$1,200.10