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	$142.87	7.745%	$153.9353	$153.94	$153.95	$153.90
Purchase #2	$215.59	4.588%	$225.4813	$225.48	$225.50	$225.50
Purchase #3	$49.47	10.143%	$54.4877	$54.49	$54.50	$54.50
Purchase #4	$83.95	6.786%	$89.6468	$89.65	$89.65	$89.60
Purchase #5	$112.47	12.171%	$126.1587	$126.16	$126.15	$126.20
Purchase #6	$234.55	5.152%	$246.634	$246.63	$246.65	$246.60
Purchase #7	$156.69	11.630%	$174.913	$174.91	$174.90	$174.90
7 purchase totals =	$995.59		$1,071.2568	$1,071.26	$1,071.30	$1,071.20