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	$88.31	9.287%	$96.5113	$96.51	$96.50	$96.50
Purchase #2	$66.26	6.423%	$70.5159	$70.52	$70.50	$70.50
Purchase #3	$238.27	8.194%	$257.7938	$257.79	$257.80	$257.80
Purchase #4	$208.79	12.551%	$234.9952	$235.00	$235.00	$235.00
Purchase #5	$81.96	10.504%	$90.5691	$90.57	$90.55	$90.60
Purchase #6	$219.79	8.599%	$238.6897	$238.69	$238.70	$238.70
Purchase #7	$189.79	3.674%	$196.7629	$196.76	$196.75	$196.80
7 purchase totals =	$1,093.17		$1,185.8379	$1,185.84	$1,185.80	$1,185.90