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	$147.79	13.377%	$167.5599	$167.56	$167.55	$167.60
Purchase #2	$67.66	7.147%	$72.4957	$72.50	$72.50	$72.50
Purchase #3	$38.84	12.870%	$43.8387	$43.84	$43.85	$43.80
Purchase #4	$94.37	5.476%	$99.5377	$99.54	$99.55	$99.50
Purchase #5	$128.32	10.258%	$141.4831	$141.48	$141.50	$141.50
Purchase #6	$29.48	11.420%	$32.8466	$32.85	$32.85	$32.80
Purchase #7	$32.69	5.324%	$34.4304	$34.43	$34.45	$34.40
7 purchase totals =	$539.15		$592.1921	$592.20	$592.25	$592.10