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	$214.76	4.786%	$225.0384	$225.04	$225.05	$225.00
Purchase #2	$49.29	10.709%	$54.5685	$54.57	$54.55	$54.60
Purchase #3	$50.62	11.384%	$56.3826	$56.38	$56.40	$56.40
Purchase #4	$230.40	4.401%	$240.5399	$240.54	$240.55	$240.50
Purchase #5	$242.82	9.810%	$266.6406	$266.64	$266.65	$266.60
Purchase #6	$117.45	9.548%	$128.6641	$128.66	$128.65	$128.70
Purchase #7	$186.28	12.137%	$208.8888	$208.89	$208.90	$208.90
7 purchase totals =	$1,091.62		$1,180.7229	$1,180.72	$1,180.75	$1,180.70