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	$162.30	5.802%	$171.7166	$171.72	$171.70	$171.70
Purchase #2	$246.36	5.783%	$260.607	$260.61	$260.60	$260.60
Purchase #3	$34.58	8.746%	$37.6044	$37.60	$37.60	$37.60
Purchase #4	$148.93	9.224%	$162.6673	$162.67	$162.65	$162.70
Purchase #5	$164.38	3.784%	$170.6001	$170.60	$170.60	$170.60
Purchase #6	$210.32	7.370%	$225.8206	$225.82	$225.80	$225.80
Purchase #7	$72.98	7.553%	$78.4922	$78.49	$78.50	$78.50
7 purchase totals =	$1,039.85		$1,107.5082	$1,107.51	$1,107.45	$1,107.50