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	$64.96	3.538%	$67.2583	$67.26	$67.25	$67.30
Purchase #2	$147.85	7.489%	$158.9225	$158.92	$158.90	$158.90
Purchase #3	$95.95	3.429%	$99.2401	$99.24	$99.25	$99.20
Purchase #4	$30.37	4.274%	$31.668	$31.67	$31.65	$31.70
Purchase #5	$222.87	3.419%	$230.4899	$230.49	$230.50	$230.50
Purchase #6	$250.90	5.752%	$265.3318	$265.33	$265.35	$265.30
Purchase #7	$54.83	13.334%	$62.141	$62.14	$62.15	$62.10
7 purchase totals =	$867.73		$915.0516	$915.05	$915.05	$915.00