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	$43.38	7.215%	$46.5099	$46.51	$46.50	$46.50
Purchase #2	$58.60	13.451%	$66.4823	$66.48	$66.50	$66.50
Purchase #3	$185.96	7.732%	$200.3384	$200.34	$200.35	$200.30
Purchase #4	$128.25	11.317%	$142.7641	$142.76	$142.75	$142.80
Purchase #5	$185.49	6.306%	$197.187	$197.19	$197.20	$197.20
Purchase #6	$124.95	12.874%	$141.0361	$141.04	$141.05	$141.00
Purchase #7	$46.55	12.390%	$52.3175	$52.32	$52.30	$52.30
7 purchase totals =	$773.18		$846.6353	$846.64	$846.65	$846.60