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	$206.40	10.453%	$227.975	$227.98	$228.00	$228.00
Purchase #2	$67.28	5.447%	$70.9447	$70.94	$70.95	$70.90
Purchase #3	$214.44	3.674%	$222.3185	$222.32	$222.30	$222.30
Purchase #4	$179.54	4.181%	$187.0466	$187.05	$187.05	$187.00
Purchase #5	$227.60	4.276%	$237.3322	$237.33	$237.35	$237.30
Purchase #6	$65.63	3.484%	$67.9165	$67.92	$67.90	$67.90
Purchase #7	$237.71	9.330%	$259.8883	$259.89	$259.90	$259.90
7 purchase totals =	$1,198.60		$1,273.4218	$1,273.43	$1,273.45	$1,273.30