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	$201.64	11.646%	$225.123	$225.12	$225.10	$225.10
Purchase #2	$139.75	4.135%	$145.5287	$145.53	$145.55	$145.50
Purchase #3	$102.77	11.595%	$114.6862	$114.69	$114.70	$114.70
Purchase #4	$58.83	9.688%	$64.5295	$64.53	$64.55	$64.50
Purchase #5	$112.92	3.203%	$116.5368	$116.54	$116.55	$116.50
Purchase #6	$99.76	13.310%	$113.0381	$113.04	$113.05	$113.00
Purchase #7	$213.58	12.332%	$239.9187	$239.92	$239.90	$239.90
7 purchase totals =	$929.25		$1,019.3610	$1,019.37	$1,019.40	$1,019.20