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	$193.95	12.570%	$218.3295	$218.33	$218.35	$218.30
Purchase #2	$225.40	6.762%	$240.6415	$240.64	$240.65	$240.60
Purchase #3	$169.89	5.333%	$178.9502	$178.95	$178.95	$179.00
Purchase #4	$227.57	5.807%	$240.785	$240.79	$240.80	$240.80
Purchase #5	$57.38	9.444%	$62.799	$62.80	$62.80	$62.80
Purchase #6	$17.48	9.546%	$19.1486	$19.15	$19.15	$19.10
Purchase #7	$81.61	11.194%	$90.7454	$90.75	$90.75	$90.70
7 purchase totals =	$973.28		$1,051.3992	$1,051.41	$1,051.45	$1,051.30