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	$179.78	5.813%	$190.2306	$190.23	$190.25	$190.20
Purchase #2	$184.33	3.214%	$190.2544	$190.25	$190.25	$190.30
Purchase #3	$118.54	12.351%	$133.1809	$133.18	$133.20	$133.20
Purchase #4	$151.99	11.664%	$169.7181	$169.72	$169.70	$169.70
Purchase #5	$171.33	13.699%	$194.8005	$194.80	$194.80	$194.80
Purchase #6	$250.85	13.612%	$284.9957	$285.00	$285.00	$285.00
Purchase #7	$74.90	10.193%	$82.5346	$82.53	$82.55	$82.50
7 purchase totals =	$1,131.72		$1,245.7148	$1,245.71	$1,245.75	$1,245.70