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	$221.34	11.334%	$246.4267	$246.43	$246.45	$246.40
Purchase #2	$92.97	7.270%	$99.7289	$99.73	$99.75	$99.70
Purchase #3	$109.50	12.683%	$123.3879	$123.39	$123.40	$123.40
Purchase #4	$41.30	11.580%	$46.0825	$46.08	$46.10	$46.10
Purchase #5	$36.25	3.140%	$37.3883	$37.39	$37.40	$37.40
Purchase #6	$94.25	9.544%	$103.2452	$103.25	$103.25	$103.20
Purchase #7	$135.54	8.676%	$147.2995	$147.30	$147.30	$147.30
7 purchase totals =	$731.15		$803.5590	$803.57	$803.65	$803.50