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	$31.39	3.704%	$32.5527	$32.55	$32.55	$32.60
Purchase #2	$120.60	3.353%	$124.6437	$124.64	$124.65	$124.60
Purchase #3	$233.89	7.839%	$252.2246	$252.22	$252.20	$252.20
Purchase #4	$94.65	5.222%	$99.5926	$99.59	$99.60	$99.60
Purchase #5	$105.69	10.124%	$116.3901	$116.39	$116.40	$116.40
Purchase #6	$80.69	10.835%	$89.4328	$89.43	$89.45	$89.40
Purchase #7	$63.59	10.386%	$70.1945	$70.19	$70.20	$70.20
7 purchase totals =	$730.50		$785.0310	$785.01	$785.05	$785.00