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	$68.50	11.731%	$76.5357	$76.54	$76.55	$76.50
Purchase #2	$241.64	13.157%	$273.4326	$273.43	$273.45	$273.40
Purchase #3	$233.83	12.754%	$263.6527	$263.65	$263.65	$263.70
Purchase #4	$154.96	8.639%	$168.347	$168.35	$168.35	$168.30
Purchase #5	$173.32	7.596%	$186.4854	$186.49	$186.50	$186.50
Purchase #6	$25.86	7.627%	$27.8323	$27.83	$27.85	$27.80
Purchase #7	$87.26	3.640%	$90.4363	$90.44	$90.45	$90.40
7 purchase totals =	$985.37		$1,086.7220	$1,086.73	$1,086.80	$1,086.60