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	$118.37	11.300%	$131.7458	$131.75	$131.75	$131.70
Purchase #2	$118.89	4.172%	$123.8501	$123.85	$123.85	$123.90
Purchase #3	$50.55	4.214%	$52.6802	$52.68	$52.70	$52.70
Purchase #4	$220.89	3.650%	$228.9525	$228.95	$228.95	$229.00
Purchase #5	$108.98	3.837%	$113.1616	$113.16	$113.15	$113.20
Purchase #6	$74.40	8.190%	$80.4934	$80.49	$80.50	$80.50
Purchase #7	$27.52	3.306%	$28.4298	$28.43	$28.45	$28.40
7 purchase totals =	$719.60		$759.3134	$759.31	$759.35	$759.40