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	$80.94	8.237%	$87.607	$87.61	$87.60	$87.60
Purchase #2	$99.26	4.319%	$103.547	$103.55	$103.55	$103.50
Purchase #3	$128.40	6.758%	$137.0773	$137.08	$137.10	$137.10
Purchase #4	$127.50	11.658%	$142.364	$142.36	$142.35	$142.40
Purchase #5	$138.29	13.449%	$156.8886	$156.89	$156.90	$156.90
Purchase #6	$51.49	8.543%	$55.8888	$55.89	$55.90	$55.90
Purchase #7	$65.28	6.685%	$69.644	$69.64	$69.65	$69.60
7 purchase totals =	$691.16		$753.0167	$753.02	$753.05	$753.00