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	$112.56	9.771%	$123.5582	$123.56	$123.55	$123.60
Purchase #2	$204.38	5.168%	$214.9424	$214.94	$214.95	$214.90
Purchase #3	$39.67	10.666%	$43.9012	$43.90	$43.90	$43.90
Purchase #4	$85.88	11.370%	$95.6446	$95.64	$95.65	$95.60
Purchase #5	$203.61	8.806%	$221.5399	$221.54	$221.55	$221.50
Purchase #6	$56.38	7.272%	$60.48	$60.48	$60.50	$60.50
Purchase #7	$188.84	7.709%	$203.3977	$203.40	$203.40	$203.40
7 purchase totals =	$891.32		$963.4640	$963.46	$963.50	$963.40