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	$31.50	5.648%	$33.2791	$33.28	$33.30	$33.30
Purchase #2	$150.75	5.147%	$158.5091	$158.51	$158.50	$158.50
Purchase #3	$216.65	8.173%	$234.3568	$234.36	$234.35	$234.40
Purchase #4	$78.82	13.144%	$89.1801	$89.18	$89.20	$89.20
Purchase #5	$177.45	10.841%	$196.6874	$196.69	$196.70	$196.70
Purchase #6	$186.53	6.185%	$198.0669	$198.07	$198.05	$198.10
Purchase #7	$210.40	3.249%	$217.2359	$217.24	$217.25	$217.20
7 purchase totals =	$1,052.10		$1,127.3153	$1,127.33	$1,127.35	$1,127.40