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	$41.46	7.818%	$44.7013	$44.70	$44.70	$44.70
Purchase #2	$244.32	4.754%	$255.935	$255.94	$255.95	$255.90
Purchase #3	$97.67	13.732%	$111.082	$111.08	$111.10	$111.10
Purchase #4	$94.61	6.626%	$100.8789	$100.88	$100.90	$100.90
Purchase #5	$123.70	13.491%	$140.3884	$140.39	$140.40	$140.40
Purchase #6	$31.33	5.340%	$33.003	$33.00	$33.00	$33.00
Purchase #7	$6.89	4.423%	$7.1947	$7.19	$7.20	$7.20
7 purchase totals =	$639.98		$693.1833	$693.18	$693.25	$693.20