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	$225.63	13.494%	$256.0765	$256.08	$256.10	$256.10
Purchase #2	$176.61	7.284%	$189.4743	$189.47	$189.45	$189.50
Purchase #3	$113.98	8.387%	$123.5395	$123.54	$123.55	$123.50
Purchase #4	$212.37	13.838%	$241.7578	$241.76	$241.75	$241.80
Purchase #5	$152.69	8.412%	$165.5343	$165.53	$165.55	$165.50
Purchase #6	$88.67	9.266%	$96.8862	$96.89	$96.90	$96.90
Purchase #7	$114.99	10.798%	$127.4066	$127.41	$127.40	$127.40
7 purchase totals =	$1,084.94		$1,200.6752	$1,200.68	$1,200.70	$1,200.70