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	$101.88	7.127%	$109.141	$109.14	$109.15	$109.10
Purchase #2	$162.95	7.358%	$174.9399	$174.94	$174.95	$174.90
Purchase #3	$140.72	7.630%	$151.4569	$151.46	$151.45	$151.50
Purchase #4	$47.96	10.278%	$52.8893	$52.89	$52.90	$52.90
Purchase #5	$214.74	12.444%	$241.4622	$241.46	$241.45	$241.50
Purchase #6	$186.54	13.514%	$211.749	$211.75	$211.75	$211.70
Purchase #7	$222.53	3.137%	$229.5108	$229.51	$229.50	$229.50
7 purchase totals =	$1,077.32		$1,171.1491	$1,171.15	$1,171.15	$1,171.10