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	$176.94	3.430%	$183.009	$183.01	$183.00	$183.00
Purchase #2	$215.73	3.798%	$223.9234	$223.92	$223.90	$223.90
Purchase #3	$75.85	7.708%	$81.6965	$81.70	$81.70	$81.70
Purchase #4	$79.50	13.683%	$90.378	$90.38	$90.40	$90.40
Purchase #5	$27.98	3.252%	$28.8899	$28.89	$28.90	$28.90
Purchase #6	$176.34	6.532%	$187.8585	$187.86	$187.85	$187.90
Purchase #7	$204.55	9.418%	$223.8145	$223.81	$223.80	$223.80
7 purchase totals =	$956.89		$1,019.5698	$1,019.57	$1,019.55	$1,019.60