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	$142.66	5.759%	$150.8758	$150.88	$150.90	$150.90
Purchase #2	$126.37	5.320%	$133.0929	$133.09	$133.10	$133.10
Purchase #3	$36.53	6.292%	$38.8285	$38.83	$38.85	$38.80
Purchase #4	$30.83	4.721%	$32.2855	$32.29	$32.30	$32.30
Purchase #5	$49.28	6.411%	$52.4393	$52.44	$52.45	$52.40
Purchase #6	$182.89	4.725%	$191.5316	$191.53	$191.55	$191.50
Purchase #7	$195.30	11.744%	$218.236	$218.24	$218.25	$218.20
7 purchase totals =	$763.86		$817.2896	$817.30	$817.40	$817.20