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	$107.81	9.808%	$118.384	$118.38	$118.40	$118.40
Purchase #2	$108.73	10.809%	$120.4826	$120.48	$120.50	$120.50
Purchase #3	$79.59	4.861%	$83.4589	$83.46	$83.45	$83.50
Purchase #4	$92.86	5.221%	$97.7082	$97.71	$97.70	$97.70
Purchase #5	$76.90	7.327%	$82.5345	$82.53	$82.55	$82.50
Purchase #6	$108.83	4.845%	$114.1028	$114.10	$114.10	$114.10
Purchase #7	$150.48	13.458%	$170.7316	$170.73	$170.75	$170.70
7 purchase totals =	$725.20		$787.4026	$787.39	$787.45	$787.40