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	$203.88	9.162%	$222.5595	$222.56	$222.55	$222.60
Purchase #2	$160.75	4.237%	$167.561	$167.56	$167.55	$167.60
Purchase #3	$117.81	11.445%	$131.2934	$131.29	$131.30	$131.30
Purchase #4	$94.32	5.238%	$99.2605	$99.26	$99.25	$99.30
Purchase #5	$100.68	6.163%	$106.8849	$106.88	$106.90	$106.90
Purchase #6	$104.47	9.635%	$114.5357	$114.54	$114.55	$114.50
Purchase #7	$10.63	10.311%	$11.7261	$11.73	$11.75	$11.70
7 purchase totals =	$792.54		$853.8211	$853.82	$853.85	$853.90