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	$70.28	3.493%	$72.7349	$72.73	$72.75	$72.70
Purchase #2	$97.54	12.390%	$109.6252	$109.63	$109.65	$109.60
Purchase #3	$225.97	10.525%	$249.7533	$249.75	$249.75	$249.80
Purchase #4	$38.52	10.139%	$42.4255	$42.43	$42.45	$42.40
Purchase #5	$227.94	13.780%	$259.3501	$259.35	$259.35	$259.40
Purchase #6	$155.43	12.104%	$174.2432	$174.24	$174.25	$174.20
Purchase #7	$105.95	10.559%	$117.1373	$117.14	$117.15	$117.10
7 purchase totals =	$921.63		$1,025.2695	$1,025.27	$1,025.35	$1,025.20