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	$158.75	12.860%	$179.1653	$179.17	$179.15	$179.20
Purchase #2	$213.47	7.326%	$229.1088	$229.11	$229.10	$229.10
Purchase #3	$35.35	7.226%	$37.9044	$37.90	$37.90	$37.90
Purchase #4	$236.25	8.218%	$255.665	$255.67	$255.65	$255.70
Purchase #5	$176.46	12.283%	$198.1346	$198.13	$198.15	$198.10
Purchase #6	$103.83	8.176%	$112.3191	$112.32	$112.30	$112.30
Purchase #7	$57.70	11.405%	$64.2807	$64.28	$64.30	$64.30
7 purchase totals =	$981.81		$1,076.5779	$1,076.58	$1,076.55	$1,076.60