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	$204.54	4.226%	$213.1839	$213.18	$213.20	$213.20
Purchase #2	$61.37	13.587%	$69.7083	$69.71	$69.70	$69.70
Purchase #3	$124.25	12.862%	$140.231	$140.23	$140.25	$140.20
Purchase #4	$185.46	13.691%	$210.8513	$210.85	$210.85	$210.90
Purchase #5	$151.53	10.804%	$167.9013	$167.90	$167.90	$167.90
Purchase #6	$145.47	3.355%	$150.3505	$150.35	$150.35	$150.40
Purchase #7	$93.78	5.696%	$99.1217	$99.12	$99.10	$99.10
7 purchase totals =	$966.40		$1,051.3480	$1,051.34	$1,051.35	$1,051.40