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	$191.69	4.197%	$199.7352	$199.74	$199.75	$199.70
Purchase #2	$142.55	12.309%	$160.0965	$160.10	$160.10	$160.10
Purchase #3	$159.45	5.555%	$168.3074	$168.31	$168.30	$168.30
Purchase #4	$247.98	7.241%	$265.9362	$265.94	$265.95	$265.90
Purchase #5	$100.32	3.380%	$103.7108	$103.71	$103.70	$103.70
Purchase #6	$63.69	6.574%	$67.877	$67.88	$67.90	$67.90
Purchase #7	$247.85	10.248%	$273.2497	$273.25	$273.25	$273.20
7 purchase totals =	$1,153.53		$1,238.9128	$1,238.93	$1,238.95	$1,238.80