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	$206.79	10.361%	$228.2155	$228.22	$228.20	$228.20
Purchase #2	$109.37	8.252%	$118.3952	$118.40	$118.40	$118.40
Purchase #3	$29.61	6.259%	$31.4633	$31.46	$31.45	$31.50
Purchase #4	$247.83	6.260%	$263.3442	$263.34	$263.35	$263.30
Purchase #5	$165.68	8.319%	$179.4629	$179.46	$179.45	$179.50
Purchase #6	$179.52	5.836%	$189.9968	$190.00	$190.00	$190.00
Purchase #7	$109.81	12.106%	$123.1036	$123.10	$123.10	$123.10
7 purchase totals =	$1,048.61		$1,133.9815	$1,133.98	$1,133.95	$1,134.00