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	$208.38	8.406%	$225.8964	$225.90	$225.90	$225.90
Purchase #2	$138.30	11.649%	$154.4106	$154.41	$154.40	$154.40
Purchase #3	$118.38	7.735%	$127.5367	$127.54	$127.55	$127.50
Purchase #4	$51.75	12.639%	$58.2907	$58.29	$58.30	$58.30
Purchase #5	$202.86	3.655%	$210.2745	$210.27	$210.25	$210.30
Purchase #6	$158.76	7.204%	$170.1971	$170.20	$170.20	$170.20
Purchase #7	$182.40	11.786%	$203.8977	$203.90	$203.90	$203.90
7 purchase totals =	$1,060.83		$1,150.5037	$1,150.51	$1,150.50	$1,150.50