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	$250.91	7.362%	$269.382	$269.38	$269.40	$269.40
Purchase #2	$19.80	4.655%	$20.7217	$20.72	$20.70	$20.70
Purchase #3	$250.75	5.685%	$265.0051	$265.01	$265.00	$265.00
Purchase #4	$115.29	3.237%	$119.0219	$119.02	$119.00	$119.00
Purchase #5	$210.69	5.540%	$222.3622	$222.36	$222.35	$222.40
Purchase #6	$218.75	11.691%	$244.3241	$244.32	$244.30	$244.30
Purchase #7	$101.25	13.239%	$114.6545	$114.65	$114.65	$114.70
7 purchase totals =	$1,167.44		$1,255.4715	$1,255.46	$1,255.40	$1,255.50