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	$125.48	6.401%	$133.512	$133.51	$133.50	$133.50
Purchase #2	$35.47	7.564%	$38.153	$38.15	$38.15	$38.20
Purchase #3	$160.80	13.510%	$182.5241	$182.52	$182.50	$182.50
Purchase #4	$14.78	6.517%	$15.7432	$15.74	$15.75	$15.70
Purchase #5	$94.70	3.516%	$98.0297	$98.03	$98.05	$98.00
Purchase #6	$79.43	3.783%	$82.4348	$82.43	$82.45	$82.40
Purchase #7	$97.93	12.443%	$110.1154	$110.12	$110.10	$110.10
7 purchase totals =	$608.59		$660.5122	$660.50	$660.50	$660.40