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	$43.80	3.492%	$45.3295	$45.33	$45.35	$45.30
Purchase #2	$91.37	13.773%	$103.9544	$103.95	$103.95	$104.00
Purchase #3	$152.43	13.389%	$172.8389	$172.84	$172.85	$172.80
Purchase #4	$119.50	9.688%	$131.0772	$131.08	$131.10	$131.10
Purchase #5	$236.58	7.741%	$254.8937	$254.89	$254.90	$254.90
Purchase #6	$185.48	4.688%	$194.1753	$194.18	$194.20	$194.20
Purchase #7	$165.49	5.577%	$174.7194	$174.72	$174.70	$174.70
7 purchase totals =	$994.65		$1,076.9884	$1,076.99	$1,077.05	$1,077.00