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	$140.82	4.162%	$146.6809	$146.68	$146.70	$146.70
Purchase #2	$79.46	9.226%	$86.791	$86.79	$86.80	$86.80
Purchase #3	$17.98	6.285%	$19.11	$19.11	$19.10	$19.10
Purchase #4	$62.54	8.234%	$67.6895	$67.69	$67.70	$67.70
Purchase #5	$80.57	13.347%	$91.3237	$91.32	$91.30	$91.30
Purchase #6	$180.85	5.527%	$190.8456	$190.85	$190.85	$190.80
Purchase #7	$117.35	5.556%	$123.87	$123.87	$123.85	$123.90
7 purchase totals =	$679.57		$726.3107	$726.31	$726.30	$726.30