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	$24.51	4.567%	$25.6294	$25.63	$25.65	$25.60
Purchase #2	$151.90	11.140%	$168.8217	$168.82	$168.80	$168.80
Purchase #3	$149.80	12.766%	$168.9235	$168.92	$168.90	$168.90
Purchase #4	$245.31	7.144%	$262.8349	$262.83	$262.85	$262.80
Purchase #5	$58.37	3.721%	$60.5419	$60.54	$60.55	$60.50
Purchase #6	$191.91	13.721%	$218.242	$218.24	$218.25	$218.20
Purchase #7	$40.25	5.283%	$42.3764	$42.38	$42.40	$42.40
7 purchase totals =	$862.05		$947.3698	$947.36	$947.40	$947.20