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	$106.41	3.287%	$109.9077	$109.91	$109.90	$109.90
Purchase #2	$244.83	6.560%	$260.8908	$260.89	$260.90	$260.90
Purchase #3	$76.39	7.475%	$82.1002	$82.10	$82.10	$82.10
Purchase #4	$185.34	12.324%	$208.1813	$208.18	$208.20	$208.20
Purchase #5	$248.83	4.721%	$260.5773	$260.58	$260.60	$260.60
Purchase #6	$151.84	4.347%	$158.4405	$158.44	$158.45	$158.40
Purchase #7	$14.33	12.511%	$16.1228	$16.12	$16.10	$16.10
7 purchase totals =	$1,027.97		$1,096.2206	$1,096.22	$1,096.25	$1,096.20