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	$174.51	12.570%	$196.4459	$196.45	$196.45	$196.40
Purchase #2	$100.99	12.833%	$113.95	$113.95	$113.95	$114.00
Purchase #3	$31.32	4.327%	$32.6752	$32.68	$32.70	$32.70
Purchase #4	$71.97	11.781%	$80.4488	$80.45	$80.45	$80.40
Purchase #5	$73.43	6.714%	$78.3601	$78.36	$78.35	$78.40
Purchase #6	$82.88	12.200%	$92.9914	$92.99	$93.00	$93.00
Purchase #7	$39.67	12.550%	$44.6486	$44.65	$44.65	$44.60
7 purchase totals =	$574.77		$639.5200	$639.53	$639.55	$639.50