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	$207.50	9.524%	$227.2623	$227.26	$227.25	$227.30
Purchase #2	$176.38	3.210%	$182.0418	$182.04	$182.05	$182.00
Purchase #3	$47.34	11.368%	$52.7216	$52.72	$52.70	$52.70
Purchase #4	$80.46	4.345%	$83.956	$83.96	$83.95	$84.00
Purchase #5	$224.98	11.541%	$250.9449	$250.94	$250.95	$250.90
Purchase #6	$94.64	5.268%	$99.6256	$99.63	$99.65	$99.60
Purchase #7	$188.71	13.710%	$214.5821	$214.58	$214.60	$214.60
7 purchase totals =	$1,020.01		$1,111.1343	$1,111.13	$1,111.15	$1,111.10