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	$136.37	4.174%	$142.0621	$142.06	$142.05	$142.10
Purchase #2	$206.43	13.667%	$234.6428	$234.64	$234.65	$234.60
Purchase #3	$40.92	9.823%	$44.9396	$44.94	$44.95	$44.90
Purchase #4	$148.35	10.788%	$164.354	$164.35	$164.35	$164.40
Purchase #5	$67.35	6.116%	$71.4691	$71.47	$71.45	$71.50
Purchase #6	$236.48	5.419%	$249.2949	$249.29	$249.30	$249.30
Purchase #7	$202.83	9.373%	$221.8413	$221.84	$221.85	$221.80
7 purchase totals =	$1,038.73		$1,128.6038	$1,128.59	$1,128.60	$1,128.60