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	$141.79	3.654%	$146.971	$146.97	$146.95	$147.00
Purchase #2	$128.86	13.548%	$146.318	$146.32	$146.30	$146.30
Purchase #3	$79.40	5.405%	$83.6916	$83.69	$83.70	$83.70
Purchase #4	$45.30	9.185%	$49.4608	$49.46	$49.45	$49.50
Purchase #5	$31.77	12.873%	$35.8598	$35.86	$35.85	$35.90
Purchase #6	$76.25	8.108%	$82.4324	$82.43	$82.45	$82.40
Purchase #7	$190.54	9.619%	$208.868	$208.87	$208.85	$208.90
7 purchase totals =	$693.91		$753.6016	$753.60	$753.55	$753.70