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	$42.86	6.210%	$45.5216	$45.52	$45.50	$45.50
Purchase #2	$244.85	4.423%	$255.6797	$255.68	$255.70	$255.70
Purchase #3	$88.99	3.804%	$92.3752	$92.38	$92.40	$92.40
Purchase #4	$88.84	13.489%	$100.8236	$100.82	$100.80	$100.80
Purchase #5	$32.39	10.191%	$35.6909	$35.69	$35.70	$35.70
Purchase #6	$249.34	11.678%	$278.4579	$278.46	$278.45	$278.50
Purchase #7	$183.44	9.399%	$200.6815	$200.68	$200.70	$200.70
7 purchase totals =	$930.71		$1,009.2304	$1,009.23	$1,009.25	$1,009.30