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	$57.77	7.746%	$62.2449	$62.24	$62.25	$62.20
Purchase #2	$162.90	6.477%	$173.451	$173.45	$173.45	$173.50
Purchase #3	$69.66	11.304%	$77.5344	$77.53	$77.55	$77.50
Purchase #4	$208.37	8.266%	$225.5939	$225.59	$225.60	$225.60
Purchase #5	$237.29	11.747%	$265.1645	$265.16	$265.15	$265.20
Purchase #6	$79.33	7.319%	$85.1362	$85.14	$85.15	$85.10
Purchase #7	$238.81	9.610%	$261.7596	$261.76	$261.75	$261.80
7 purchase totals =	$1,054.13		$1,150.8845	$1,150.87	$1,150.90	$1,150.90