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	$140.64	13.675%	$159.8725	$159.87	$159.85	$159.90
Purchase #2	$222.64	12.296%	$250.0158	$250.02	$250.00	$250.00
Purchase #3	$156.78	10.340%	$172.9911	$172.99	$173.00	$173.00
Purchase #4	$56.81	13.543%	$64.5038	$64.50	$64.50	$64.50
Purchase #5	$141.62	9.663%	$155.3047	$155.30	$155.30	$155.30
Purchase #6	$38.41	10.500%	$42.4431	$42.44	$42.45	$42.40
Purchase #7	$152.57	12.402%	$171.4917	$171.49	$171.50	$171.50
7 purchase totals =	$909.47		$1,016.6227	$1,016.61	$1,016.60	$1,016.60