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	$147.43	11.724%	$164.7147	$164.71	$164.70	$164.70
Purchase #2	$217.89	10.848%	$241.5267	$241.53	$241.55	$241.50
Purchase #3	$40.30	5.151%	$42.3759	$42.38	$42.40	$42.40
Purchase #4	$246.71	7.456%	$265.1047	$265.10	$265.10	$265.10
Purchase #5	$181.55	4.854%	$190.3624	$190.36	$190.35	$190.40
Purchase #6	$29.51	7.801%	$31.8121	$31.81	$31.80	$31.80
Purchase #7	$69.55	3.748%	$72.1567	$72.16	$72.15	$72.20
7 purchase totals =	$932.94		$1,008.0532	$1,008.05	$1,008.05	$1,008.10