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	$186.95	5.323%	$196.9013	$196.90	$196.90	$196.90
Purchase #2	$170.34	4.338%	$177.7293	$177.73	$177.75	$177.70
Purchase #3	$148.56	13.306%	$168.3274	$168.33	$168.35	$168.30
Purchase #4	$114.94	4.305%	$119.8882	$119.89	$119.90	$119.90
Purchase #5	$155.64	8.334%	$168.611	$168.61	$168.60	$168.60
Purchase #6	$120.39	5.351%	$126.8321	$126.83	$126.85	$126.80
Purchase #7	$227.34	12.712%	$256.2395	$256.24	$256.25	$256.20
7 purchase totals =	$1,124.16		$1,214.5288	$1,214.53	$1,214.60	$1,214.40