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	$98.60	13.519%	$111.9297	$111.93	$111.95	$111.90
Purchase #2	$51.93	6.760%	$55.4405	$55.44	$55.45	$55.40
Purchase #3	$86.52	4.200%	$90.1538	$90.15	$90.15	$90.20
Purchase #4	$65.57	9.633%	$71.8864	$71.89	$71.90	$71.90
Purchase #5	$166.90	11.549%	$186.1753	$186.18	$186.20	$186.20
Purchase #6	$133.73	8.579%	$145.2027	$145.20	$145.20	$145.20
Purchase #7	$149.35	3.282%	$154.2517	$154.25	$154.25	$154.30
7 purchase totals =	$752.60		$815.0401	$815.04	$815.10	$815.10