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	$215.48	11.411%	$240.0684	$240.07	$240.05	$240.10
Purchase #2	$210.98	3.241%	$217.8179	$217.82	$217.80	$217.80
Purchase #3	$218.90	12.623%	$246.5317	$246.53	$246.55	$246.50
Purchase #4	$11.78	6.584%	$12.5556	$12.56	$12.55	$12.60
Purchase #5	$158.73	9.854%	$174.3713	$174.37	$174.35	$174.40
Purchase #6	$107.69	3.784%	$111.765	$111.77	$111.75	$111.80
Purchase #7	$156.78	13.701%	$178.2604	$178.26	$178.25	$178.30
7 purchase totals =	$1,080.34		$1,181.3703	$1,181.38	$1,181.30	$1,181.50