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	9.726%	$156.5351	$156.54	$156.55	$156.50
Purchase #2	$118.67	7.324%	$127.3614	$127.36	$127.35	$127.40
Purchase #3	$198.26	12.599%	$223.2388	$223.24	$223.25	$223.20
Purchase #4	$168.39	7.210%	$180.5309	$180.53	$180.55	$180.50
Purchase #5	$151.50	4.705%	$158.6281	$158.63	$158.65	$158.60
Purchase #6	$156.68	5.177%	$164.7913	$164.79	$164.80	$164.80
Purchase #7	$161.93	11.435%	$180.4467	$180.45	$180.45	$180.40
7 purchase totals =	$1,098.09		$1,191.5323	$1,191.54	$1,191.60	$1,191.40