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	$209.82	9.495%	$229.7424	$229.74	$229.75	$229.70
Purchase #2	$16.82	13.611%	$19.1094	$19.11	$19.10	$19.10
Purchase #3	$247.97	8.786%	$269.7566	$269.76	$269.75	$269.80
Purchase #4	$144.38	8.652%	$156.8718	$156.87	$156.85	$156.90
Purchase #5	$122.29	4.155%	$127.3711	$127.37	$127.35	$127.40
Purchase #6	$57.55	8.385%	$62.3756	$62.38	$62.40	$62.40
Purchase #7	$78.74	4.601%	$82.3628	$82.36	$82.35	$82.40
7 purchase totals =	$877.57		$947.5897	$947.59	$947.55	$947.70