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	$53.39	3.676%	$55.3526	$55.35	$55.35	$55.40
Purchase #2	$245.92	10.780%	$272.4302	$272.43	$272.45	$272.40
Purchase #3	$210.27	3.317%	$217.2447	$217.24	$217.25	$217.20
Purchase #4	$52.76	12.770%	$59.4975	$59.50	$59.50	$59.50
Purchase #5	$230.69	6.358%	$245.3573	$245.36	$245.35	$245.40
Purchase #6	$190.87	6.229%	$202.7593	$202.76	$202.75	$202.80
Purchase #7	$25.71	10.534%	$28.4183	$28.42	$28.40	$28.40
7 purchase totals =	$1,009.61		$1,081.0599	$1,081.06	$1,081.05	$1,081.10