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	$194.57	11.643%	$217.2238	$217.22	$217.20	$217.20
Purchase #2	$204.78	12.170%	$229.7017	$229.70	$229.70	$229.70
Purchase #3	$79.91	6.493%	$85.0986	$85.10	$85.10	$85.10
Purchase #4	$51.80	11.765%	$57.8943	$57.89	$57.90	$57.90
Purchase #5	$245.98	11.571%	$274.4423	$274.44	$274.45	$274.40
Purchase #6	$76.78	11.837%	$85.8684	$85.87	$85.85	$85.90
Purchase #7	$215.81	6.291%	$229.3866	$229.39	$229.40	$229.40
7 purchase totals =	$1,069.63		$1,179.6157	$1,179.61	$1,179.60	$1,179.60