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	$167.60	13.322%	$189.9277	$189.93	$189.95	$189.90
Purchase #2	$229.40	5.598%	$242.2418	$242.24	$242.25	$242.20
Purchase #3	$89.84	10.697%	$99.4502	$99.45	$99.45	$99.50
Purchase #4	$166.86	5.651%	$176.2893	$176.29	$176.30	$176.30
Purchase #5	$124.59	13.111%	$140.925	$140.93	$140.95	$140.90
Purchase #6	$190.95	11.673%	$213.2396	$213.24	$213.25	$213.20
Purchase #7	$48.53	4.526%	$50.7265	$50.73	$50.75	$50.70
7 purchase totals =	$1,017.77		$1,112.8001	$1,112.81	$1,112.90	$1,112.70