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	$58.81	6.646%	$62.7185	$62.72	$62.70	$62.70
Purchase #2	$234.90	11.463%	$261.8266	$261.83	$261.85	$261.80
Purchase #3	$104.35	6.592%	$111.2288	$111.23	$111.25	$111.20
Purchase #4	$6.95	13.856%	$7.913	$7.91	$7.90	$7.90
Purchase #5	$144.92	13.530%	$164.5277	$164.53	$164.55	$164.50
Purchase #6	$73.81	13.752%	$83.9604	$83.96	$83.95	$84.00
Purchase #7	$165.72	8.257%	$179.4035	$179.40	$179.40	$179.40
7 purchase totals =	$789.46		$871.5785	$871.58	$871.60	$871.50