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	$151.39	8.693%	$164.5503	$164.55	$164.55	$164.60
Purchase #2	$86.82	6.215%	$92.2159	$92.22	$92.20	$92.20
Purchase #3	$91.61	13.147%	$103.654	$103.65	$103.65	$103.70
Purchase #4	$38.45	11.179%	$42.7483	$42.75	$42.75	$42.70
Purchase #5	$108.87	5.584%	$114.9493	$114.95	$114.95	$114.90
Purchase #6	$28.96	6.193%	$30.7535	$30.75	$30.75	$30.80
Purchase #7	$179.65	11.659%	$200.5954	$200.60	$200.60	$200.60
7 purchase totals =	$685.75		$749.4667	$749.47	$749.45	$749.50