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	$111.95	5.677%	$118.3054	$118.31	$118.30	$118.30
Purchase #2	$78.54	9.399%	$85.922	$85.92	$85.90	$85.90
Purchase #3	$150.52	13.310%	$170.5542	$170.55	$170.55	$170.60
Purchase #4	$80.95	7.379%	$86.9233	$86.92	$86.90	$86.90
Purchase #5	$81.96	9.547%	$89.7847	$89.78	$89.80	$89.80
Purchase #6	$150.49	3.610%	$155.9227	$155.92	$155.90	$155.90
Purchase #7	$207.52	6.302%	$220.5979	$220.60	$220.60	$220.60
7 purchase totals =	$861.93		$928.0102	$928.00	$927.95	$928.00