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	$101.73	9.165%	$111.0536	$111.05	$111.05	$111.10
Purchase #2	$178.80	6.809%	$190.9745	$190.97	$190.95	$191.00
Purchase #3	$63.37	7.202%	$67.9339	$67.93	$67.95	$67.90
Purchase #4	$108.40	4.362%	$113.1284	$113.13	$113.15	$113.10
Purchase #5	$129.48	13.294%	$146.6931	$146.69	$146.70	$146.70
Purchase #6	$190.55	13.199%	$215.7007	$215.70	$215.70	$215.70
Purchase #7	$29.90	5.326%	$31.4925	$31.49	$31.50	$31.50
7 purchase totals =	$802.23		$876.9767	$876.96	$877.00	$877.00