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	$46.86	5.517%	$49.4453	$49.45	$49.45	$49.40
Purchase #2	$219.32	8.767%	$238.5478	$238.55	$238.55	$238.50
Purchase #3	$36.26	3.407%	$37.4954	$37.50	$37.50	$37.50
Purchase #4	$50.40	12.617%	$56.759	$56.76	$56.75	$56.80
Purchase #5	$200.89	10.308%	$221.5977	$221.60	$221.60	$221.60
Purchase #6	$249.92	12.756%	$281.7998	$281.80	$281.80	$281.80
Purchase #7	$56.86	6.819%	$60.7373	$60.74	$60.75	$60.70
7 purchase totals =	$860.51		$946.3823	$946.40	$946.40	$946.30