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	$28.68	7.690%	$30.8855	$30.89	$30.90	$30.90
Purchase #2	$145.80	6.303%	$154.9898	$154.99	$155.00	$155.00
Purchase #3	$168.38	10.150%	$185.4706	$185.47	$185.45	$185.50
Purchase #4	$60.94	4.365%	$63.6	$63.60	$63.60	$63.60
Purchase #5	$185.98	8.779%	$202.3072	$202.31	$202.30	$202.30
Purchase #6	$224.54	13.806%	$255.54	$255.54	$255.55	$255.50
Purchase #7	$223.60	4.432%	$233.51	$233.51	$233.50	$233.50
7 purchase totals =	$1,037.92		$1,126.3031	$1,126.31	$1,126.30	$1,126.30