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	$30.94	4.444%	$32.315	$32.32	$32.30	$32.30
Purchase #2	$115.58	12.392%	$129.9027	$129.90	$129.90	$129.90
Purchase #3	$203.46	4.149%	$211.9016	$211.90	$211.90	$211.90
Purchase #4	$118.42	8.177%	$128.1032	$128.10	$128.10	$128.10
Purchase #5	$198.55	3.844%	$206.1823	$206.18	$206.20	$206.20
Purchase #6	$131.33	8.547%	$142.5548	$142.55	$142.55	$142.60
Purchase #7	$155.61	7.612%	$167.455	$167.46	$167.45	$167.50
7 purchase totals =	$953.89		$1,018.4146	$1,018.41	$1,018.40	$1,018.50