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	$45.63	6.416%	$48.5576	$48.56	$48.55	$48.60
Purchase #2	$59.65	13.231%	$67.5423	$67.54	$67.55	$67.50
Purchase #3	$242.94	5.648%	$256.6613	$256.66	$256.65	$256.70
Purchase #4	$142.97	11.466%	$159.3629	$159.36	$159.35	$159.40
Purchase #5	$117.97	11.766%	$131.8504	$131.85	$131.85	$131.90
Purchase #6	$122.73	3.127%	$126.5678	$126.57	$126.55	$126.60
Purchase #7	$212.66	6.674%	$226.8529	$226.85	$226.85	$226.90
7 purchase totals =	$944.55		$1,017.3952	$1,017.39	$1,017.35	$1,017.60