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	$131.51	3.456%	$136.055	$136.06	$136.05	$136.10
Purchase #2	$173.88	12.870%	$196.2584	$196.26	$196.25	$196.30
Purchase #3	$219.77	5.356%	$231.5409	$231.54	$231.55	$231.50
Purchase #4	$12.31	6.450%	$13.104	$13.10	$13.10	$13.10
Purchase #5	$67.50	6.779%	$72.0758	$72.08	$72.10	$72.10
Purchase #6	$151.40	3.766%	$157.1017	$157.10	$157.10	$157.10
Purchase #7	$95.51	3.866%	$99.2024	$99.20	$99.20	$99.20
7 purchase totals =	$851.88		$905.3382	$905.34	$905.35	$905.40