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	$220.54	12.423%	$247.9377	$247.94	$247.95	$247.90
Purchase #2	$76.39	5.704%	$80.7473	$80.75	$80.75	$80.70
Purchase #3	$59.41	13.539%	$67.4535	$67.45	$67.45	$67.50
Purchase #4	$19.89	9.187%	$21.7173	$21.72	$21.70	$21.70
Purchase #5	$174.83	9.471%	$191.3881	$191.39	$191.40	$191.40
Purchase #6	$241.50	9.736%	$265.0124	$265.01	$265.00	$265.00
Purchase #7	$203.33	12.739%	$229.2322	$229.23	$229.25	$229.20
7 purchase totals =	$995.89		$1,103.4885	$1,103.49	$1,103.50	$1,103.40