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	$11.71	5.367%	$12.3385	$12.34	$12.35	$12.30
Purchase #2	$12.64	6.328%	$13.4399	$13.44	$13.45	$13.40
Purchase #3	$173.79	13.257%	$196.8293	$196.83	$196.85	$196.80
Purchase #4	$104.56	6.453%	$111.3073	$111.31	$111.30	$111.30
Purchase #5	$184.44	8.642%	$200.3793	$200.38	$200.40	$200.40
Purchase #6	$45.49	8.799%	$49.4927	$49.49	$49.50	$49.50
Purchase #7	$89.53	10.537%	$98.9638	$98.96	$98.95	$99.00
7 purchase totals =	$622.16		$682.7508	$682.75	$682.80	$682.70