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	$167.52	6.571%	$178.5277	$178.53	$178.55	$178.50
Purchase #2	$210.69	6.526%	$224.4396	$224.44	$224.45	$224.40
Purchase #3	$48.51	11.762%	$54.2157	$54.22	$54.20	$54.20
Purchase #4	$148.67	5.209%	$156.4142	$156.41	$156.40	$156.40
Purchase #5	$188.48	11.595%	$210.3343	$210.33	$210.35	$210.30
Purchase #6	$228.27	9.668%	$250.3391	$250.34	$250.35	$250.30
Purchase #7	$23.68	7.710%	$25.5057	$25.51	$25.50	$25.50
7 purchase totals =	$1,015.82		$1,099.7763	$1,099.78	$1,099.80	$1,099.60