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	$100.51	4.690%	$105.2239	$105.22	$105.20	$105.20
Purchase #2	$13.63	4.119%	$14.1914	$14.19	$14.20	$14.20
Purchase #3	$235.86	12.509%	$265.3637	$265.36	$265.35	$265.40
Purchase #4	$103.98	3.696%	$107.8231	$107.82	$107.80	$107.80
Purchase #5	$131.82	7.166%	$141.2662	$141.27	$141.25	$141.30
Purchase #6	$144.58	5.449%	$152.4582	$152.46	$152.45	$152.50
Purchase #7	$227.54	13.779%	$258.8927	$258.89	$258.90	$258.90
7 purchase totals =	$957.92		$1,045.2192	$1,045.21	$1,045.15	$1,045.30