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	$98.26	6.380%	$104.529	$104.53	$104.55	$104.50
Purchase #2	$62.26	5.184%	$65.4876	$65.49	$65.50	$65.50
Purchase #3	$59.87	12.567%	$67.3939	$67.39	$67.40	$67.40
Purchase #4	$238.44	7.309%	$255.8676	$255.87	$255.85	$255.90
Purchase #5	$40.43	10.688%	$44.7512	$44.75	$44.75	$44.80
Purchase #6	$106.32	11.838%	$118.9062	$118.91	$118.90	$118.90
Purchase #7	$129.71	10.632%	$143.5008	$143.50	$143.50	$143.50
7 purchase totals =	$735.29		$800.4363	$800.44	$800.45	$800.50