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	$11.61	8.443%	$12.5902	$12.59	$12.60	$12.60
Purchase #2	$127.79	5.208%	$134.4453	$134.45	$134.45	$134.40
Purchase #3	$120.76	4.493%	$126.1857	$126.19	$126.20	$126.20
Purchase #4	$240.81	11.267%	$267.9421	$267.94	$267.95	$267.90
Purchase #5	$57.64	7.781%	$62.125	$62.13	$62.15	$62.10
Purchase #6	$209.89	9.498%	$229.8254	$229.83	$229.85	$229.80
Purchase #7	$135.71	7.220%	$145.5083	$145.51	$145.50	$145.50
7 purchase totals =	$904.21		$978.6220	$978.64	$978.70	$978.50