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	$32.34	4.574%	$33.8192	$33.82	$33.80	$33.80
Purchase #2	$18.80	4.346%	$19.617	$19.62	$19.60	$19.60
Purchase #3	$125.67	8.488%	$136.3369	$136.34	$136.35	$136.30
Purchase #4	$134.73	5.867%	$142.6346	$142.63	$142.65	$142.60
Purchase #5	$88.61	6.413%	$94.2926	$94.29	$94.30	$94.30
Purchase #6	$215.83	12.812%	$243.4821	$243.48	$243.50	$243.50
Purchase #7	$238.29	10.592%	$263.5297	$263.53	$263.55	$263.50
7 purchase totals =	$854.27		$933.7121	$933.71	$933.75	$933.60