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	$46.40	7.600%	$49.9264	$49.93	$49.95	$49.90
Purchase #2	$134.25	12.168%	$150.5855	$150.59	$150.60	$150.60
Purchase #3	$250.90	9.575%	$274.9237	$274.92	$274.90	$274.90
Purchase #4	$129.54	11.336%	$144.2247	$144.22	$144.20	$144.20
Purchase #5	$151.56	11.165%	$168.4817	$168.48	$168.50	$168.50
Purchase #6	$86.75	6.756%	$92.6108	$92.61	$92.60	$92.60
Purchase #7	$201.82	12.381%	$226.8073	$226.81	$226.80	$226.80
7 purchase totals =	$1,001.22		$1,107.5601	$1,107.56	$1,107.55	$1,107.50