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	$222.75	5.754%	$235.567	$235.57	$235.55	$235.60
Purchase #2	$52.73	13.640%	$59.9224	$59.92	$59.90	$59.90
Purchase #3	$154.61	11.737%	$172.7566	$172.76	$172.75	$172.80
Purchase #4	$128.81	6.691%	$137.4287	$137.43	$137.45	$137.40
Purchase #5	$89.84	9.825%	$98.6668	$98.67	$98.65	$98.70
Purchase #6	$110.68	6.333%	$117.6894	$117.69	$117.70	$117.70
Purchase #7	$166.43	10.502%	$183.9085	$183.91	$183.90	$183.90
7 purchase totals =	$925.85		$1,005.9394	$1,005.95	$1,005.90	$1,006.00