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	$246.43	6.854%	$263.3203	$263.32	$263.30	$263.30
Purchase #2	$208.34	6.601%	$222.0925	$222.09	$222.10	$222.10
Purchase #3	$5.96	7.391%	$6.4005	$6.40	$6.40	$6.40
Purchase #4	$139.86	12.125%	$156.818	$156.82	$156.80	$156.80
Purchase #5	$191.40	5.680%	$202.2715	$202.27	$202.25	$202.30
Purchase #6	$64.59	12.758%	$72.8304	$72.83	$72.85	$72.80
Purchase #7	$185.70	11.771%	$207.5587	$207.56	$207.55	$207.60
7 purchase totals =	$1,042.28		$1,131.2919	$1,131.29	$1,131.25	$1,131.30