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	$40.94	12.237%	$45.9498	$45.95	$45.95	$45.90
Purchase #2	$133.70	12.368%	$150.236	$150.24	$150.25	$150.20
Purchase #3	$164.89	4.618%	$172.5046	$172.50	$172.50	$172.50
Purchase #4	$174.72	6.675%	$186.3826	$186.38	$186.40	$186.40
Purchase #5	$128.35	6.825%	$137.1099	$137.11	$137.10	$137.10
Purchase #6	$27.92	9.283%	$30.5118	$30.51	$30.50	$30.50
Purchase #7	$18.75	5.643%	$19.8081	$19.81	$19.80	$19.80
7 purchase totals =	$689.27		$742.5028	$742.50	$742.50	$742.40