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	$87.88	5.756%	$92.9384	$92.94	$92.95	$92.90
Purchase #2	$224.84	11.560%	$250.8315	$250.83	$250.85	$250.80
Purchase #3	$130.29	5.864%	$137.9302	$137.93	$137.95	$137.90
Purchase #4	$240.67	12.737%	$271.3241	$271.32	$271.30	$271.30
Purchase #5	$140.84	13.516%	$159.8759	$159.88	$159.90	$159.90
Purchase #6	$7.59	4.154%	$7.9053	$7.91	$7.90	$7.90
Purchase #7	$168.46	3.345%	$174.095	$174.10	$174.10	$174.10
7 purchase totals =	$1,000.57		$1,094.9004	$1,094.91	$1,094.95	$1,094.80