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	$145.82	12.488%	$164.03	$164.03	$164.05	$164.00
Purchase #2	$16.83	11.458%	$18.7584	$18.76	$18.75	$18.80
Purchase #3	$143.42	3.221%	$148.0396	$148.04	$148.05	$148.00
Purchase #4	$180.90	9.495%	$198.0765	$198.08	$198.10	$198.10
Purchase #5	$216.51	12.311%	$243.1645	$243.16	$243.15	$243.20
Purchase #6	$154.80	9.680%	$169.7846	$169.78	$169.80	$169.80
Purchase #7	$39.84	6.736%	$42.5236	$42.52	$42.50	$42.50
7 purchase totals =	$898.12		$984.3772	$984.37	$984.40	$984.40