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	$42.57	9.744%	$46.718	$46.72	$46.70	$46.70
Purchase #2	$39.44	10.171%	$43.4514	$43.45	$43.45	$43.50
Purchase #3	$96.82	6.855%	$103.457	$103.46	$103.45	$103.50
Purchase #4	$230.79	5.639%	$243.8042	$243.80	$243.80	$243.80
Purchase #5	$103.71	8.149%	$112.1613	$112.16	$112.15	$112.20
Purchase #6	$204.96	7.513%	$220.3586	$220.36	$220.35	$220.40
Purchase #7	$109.47	7.215%	$117.3683	$117.37	$117.35	$117.40
7 purchase totals =	$827.76		$887.3188	$887.32	$887.25	$887.50