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	$159.41	5.597%	$168.3322	$168.33	$168.35	$168.30
Purchase #2	$35.40	3.131%	$36.5084	$36.51	$36.50	$36.50
Purchase #3	$37.48	12.337%	$42.1039	$42.10	$42.10	$42.10
Purchase #4	$164.79	10.764%	$182.528	$182.53	$182.55	$182.50
Purchase #5	$119.67	10.856%	$132.6614	$132.66	$132.65	$132.70
Purchase #6	$140.37	12.849%	$158.4061	$158.41	$158.40	$158.40
Purchase #7	$203.95	3.613%	$211.3187	$211.32	$211.30	$211.30
7 purchase totals =	$861.07		$931.8587	$931.86	$931.85	$931.80