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	$134.47	5.112%	$141.3441	$141.34	$141.35	$141.30
Purchase #2	$92.51	8.391%	$100.2725	$100.27	$100.25	$100.30
Purchase #3	$109.75	10.447%	$121.2156	$121.22	$121.20	$121.20
Purchase #4	$224.55	4.110%	$233.779	$233.78	$233.80	$233.80
Purchase #5	$88.59	7.805%	$95.5044	$95.50	$95.50	$95.50
Purchase #6	$92.66	11.392%	$103.2158	$103.22	$103.20	$103.20
Purchase #7	$99.80	6.178%	$105.9656	$105.97	$105.95	$106.00
7 purchase totals =	$842.33		$901.2970	$901.30	$901.25	$901.30