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	$219.96	10.441%	$242.926	$242.93	$242.95	$242.90
Purchase #2	$238.60	7.226%	$255.8412	$255.84	$255.85	$255.80
Purchase #3	$181.87	3.838%	$188.8502	$188.85	$188.85	$188.90
Purchase #4	$205.58	13.135%	$232.5829	$232.58	$232.60	$232.60
Purchase #5	$123.58	6.714%	$131.8772	$131.88	$131.90	$131.90
Purchase #6	$91.98	8.508%	$99.8057	$99.81	$99.80	$99.80
Purchase #7	$121.48	7.821%	$130.981	$130.98	$131.00	$131.00
7 purchase totals =	$1,183.05		$1,282.8642	$1,282.87	$1,282.95	$1,282.90