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	$89.47	4.697%	$93.6724	$93.67	$93.65	$93.70
Purchase #2	$94.49	13.838%	$107.5655	$107.57	$107.55	$107.60
Purchase #3	$242.47	6.670%	$258.6427	$258.64	$258.65	$258.60
Purchase #4	$172.36	7.864%	$185.9144	$185.91	$185.90	$185.90
Purchase #5	$33.42	12.829%	$37.7075	$37.71	$37.70	$37.70
Purchase #6	$172.27	4.674%	$180.3219	$180.32	$180.30	$180.30
Purchase #7	$88.35	11.795%	$98.7709	$98.77	$98.75	$98.80
7 purchase totals =	$892.83		$962.5953	$962.59	$962.50	$962.60