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	$187.50	12.298%	$210.5588	$210.56	$210.55	$210.60
Purchase #2	$227.88	4.705%	$238.6018	$238.60	$238.60	$238.60
Purchase #3	$10.77	10.134%	$11.8614	$11.86	$11.85	$11.90
Purchase #4	$85.71	7.285%	$91.954	$91.95	$91.95	$92.00
Purchase #5	$178.46	3.849%	$185.3289	$185.33	$185.35	$185.30
Purchase #6	$190.72	7.114%	$204.2878	$204.29	$204.30	$204.30
Purchase #7	$172.28	3.195%	$177.7843	$177.78	$177.80	$177.80
7 purchase totals =	$1,053.32		$1,120.3770	$1,120.37	$1,120.40	$1,120.50