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	$123.42	7.520%	$132.7012	$132.70	$132.70	$132.70
Purchase #2	$85.50	8.308%	$92.6033	$92.60	$92.60	$92.60
Purchase #3	$59.63	9.867%	$65.5137	$65.51	$65.50	$65.50
Purchase #4	$72.42	13.698%	$82.3401	$82.34	$82.35	$82.30
Purchase #5	$158.40	12.570%	$178.3109	$178.31	$178.30	$178.30
Purchase #6	$25.98	13.581%	$29.5083	$29.51	$29.50	$29.50
Purchase #7	$95.49	6.632%	$101.8229	$101.82	$101.80	$101.80
7 purchase totals =	$620.84		$682.8004	$682.79	$682.75	$682.70