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	$102.27	11.665%	$114.1998	$114.20	$114.20	$114.20
Purchase #2	$55.90	6.448%	$59.5044	$59.50	$59.50	$59.50
Purchase #3	$210.66	5.521%	$222.2905	$222.29	$222.30	$222.30
Purchase #4	$197.26	5.809%	$208.7188	$208.72	$208.70	$208.70
Purchase #5	$185.25	10.450%	$204.6086	$204.61	$204.60	$204.60
Purchase #6	$76.94	7.635%	$82.8144	$82.81	$82.80	$82.80
Purchase #7	$127.50	10.289%	$140.6185	$140.62	$140.60	$140.60
7 purchase totals =	$955.78		$1,032.7550	$1,032.75	$1,032.70	$1,032.70