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	$158.99	5.571%	$167.8473	$167.85	$167.85	$167.80
Purchase #2	$67.77	8.789%	$73.7263	$73.73	$73.75	$73.70
Purchase #3	$157.28	4.834%	$164.8829	$164.88	$164.90	$164.90
Purchase #4	$96.70	3.202%	$99.7963	$99.80	$99.80	$99.80
Purchase #5	$199.93	11.699%	$223.3198	$223.32	$223.30	$223.30
Purchase #6	$250.71	6.472%	$266.936	$266.94	$266.95	$266.90
Purchase #7	$133.81	8.295%	$144.9095	$144.91	$144.90	$144.90
7 purchase totals =	$1,065.19		$1,141.4181	$1,141.43	$1,141.45	$1,141.30