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	$71.41	11.651%	$79.73	$79.73	$79.75	$79.70
Purchase #2	$167.55	13.693%	$190.4926	$190.49	$190.50	$190.50
Purchase #3	$165.90	4.605%	$173.5397	$173.54	$173.55	$173.50
Purchase #4	$191.34	4.208%	$199.3916	$199.39	$199.40	$199.40
Purchase #5	$150.38	11.149%	$167.1459	$167.15	$167.15	$167.10
Purchase #6	$166.95	11.551%	$186.2344	$186.23	$186.25	$186.20
Purchase #7	$201.74	12.287%	$226.5278	$226.53	$226.55	$226.50
7 purchase totals =	$1,115.27		$1,223.0620	$1,223.06	$1,223.15	$1,222.90