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	$12.59	6.235%	$13.375	$13.38	$13.40	$13.40
Purchase #2	$44.59	12.536%	$50.1798	$50.18	$50.20	$50.20
Purchase #3	$81.59	10.246%	$89.9497	$89.95	$89.95	$89.90
Purchase #4	$204.37	7.366%	$219.4239	$219.42	$219.40	$219.40
Purchase #5	$181.37	6.620%	$193.3767	$193.38	$193.40	$193.40
Purchase #6	$199.63	11.309%	$222.2062	$222.21	$222.20	$222.20
Purchase #7	$82.73	4.705%	$86.6224	$86.62	$86.60	$86.60
7 purchase totals =	$806.87		$875.1337	$875.14	$875.15	$875.10