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	$198.57	11.573%	$221.5505	$221.55	$221.55	$221.60
Purchase #2	$229.48	12.829%	$258.92	$258.92	$258.90	$258.90
Purchase #3	$110.56	6.327%	$117.5551	$117.56	$117.55	$117.60
Purchase #4	$40.48	10.246%	$44.6276	$44.63	$44.65	$44.60
Purchase #5	$68.51	4.329%	$71.4758	$71.48	$71.50	$71.50
Purchase #6	$209.71	5.812%	$221.8983	$221.90	$221.90	$221.90
Purchase #7	$162.71	6.664%	$173.553	$173.55	$173.55	$173.60
7 purchase totals =	$1,020.02		$1,109.5803	$1,109.59	$1,109.60	$1,109.70