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	$41.95	3.277%	$43.3247	$43.32	$43.30	$43.30
Purchase #2	$144.60	9.375%	$158.1563	$158.16	$158.15	$158.20
Purchase #3	$180.61	8.528%	$196.0124	$196.01	$196.00	$196.00
Purchase #4	$41.74	5.474%	$44.0248	$44.02	$44.00	$44.00
Purchase #5	$154.44	7.275%	$165.6755	$165.68	$165.70	$165.70
Purchase #6	$126.30	13.797%	$143.7256	$143.73	$143.75	$143.70
Purchase #7	$128.46	12.376%	$144.3582	$144.36	$144.35	$144.40
7 purchase totals =	$818.10		$895.2775	$895.28	$895.25	$895.30