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	$124.43	3.277%	$128.5076	$128.51	$128.50	$128.50
Purchase #2	$123.43	6.237%	$131.1283	$131.13	$131.15	$131.10
Purchase #3	$175.36	3.840%	$182.0938	$182.09	$182.10	$182.10
Purchase #4	$22.25	3.129%	$22.9462	$22.95	$22.95	$22.90
Purchase #5	$109.60	4.499%	$114.5309	$114.53	$114.55	$114.50
Purchase #6	$18.42	9.210%	$20.1165	$20.12	$20.10	$20.10
Purchase #7	$115.59	3.580%	$119.7281	$119.73	$119.75	$119.70
7 purchase totals =	$689.08		$719.0514	$719.06	$719.10	$718.90