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	$109.35	3.214%	$112.8645	$112.86	$112.85	$112.90
Purchase #2	$132.86	9.274%	$145.1814	$145.18	$145.20	$145.20
Purchase #3	$45.92	8.644%	$49.8893	$49.89	$49.90	$49.90
Purchase #4	$96.36	4.498%	$100.6943	$100.69	$100.70	$100.70
Purchase #5	$106.50	5.806%	$112.6834	$112.68	$112.70	$112.70
Purchase #6	$186.52	5.421%	$196.6312	$196.63	$196.65	$196.60
Purchase #7	$21.77	4.535%	$22.7573	$22.76	$22.75	$22.80
7 purchase totals =	$699.28		$740.7014	$740.69	$740.75	$740.80