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	$139.38	11.155%	$154.9278	$154.93	$154.95	$154.90
Purchase #2	$140.47	3.547%	$145.4525	$145.45	$145.45	$145.50
Purchase #3	$158.95	7.231%	$170.4437	$170.44	$170.45	$170.40
Purchase #4	$27.76	3.617%	$28.7641	$28.76	$28.75	$28.80
Purchase #5	$71.30	9.812%	$78.296	$78.30	$78.30	$78.30
Purchase #6	$100.41	5.297%	$105.7287	$105.73	$105.75	$105.70
Purchase #7	$197.74	9.401%	$216.3295	$216.33	$216.35	$216.30
7 purchase totals =	$836.01		$899.9423	$899.94	$900.00	$899.90