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	$140.40	6.765%	$149.8981	$149.90	$149.90	$149.90
Purchase #2	$192.38	12.257%	$215.96	$215.96	$215.95	$216.00
Purchase #3	$155.56	7.387%	$167.0512	$167.05	$167.05	$167.10
Purchase #4	$51.43	13.849%	$58.5525	$58.55	$58.55	$58.60
Purchase #5	$105.83	10.445%	$116.8839	$116.88	$116.90	$116.90
Purchase #6	$143.56	6.515%	$152.9129	$152.91	$152.90	$152.90
Purchase #7	$141.49	6.698%	$150.967	$150.97	$150.95	$151.00
7 purchase totals =	$930.65		$1,012.2256	$1,012.22	$1,012.20	$1,012.40