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	$186.50	8.809%	$202.9288	$202.93	$202.95	$202.90
Purchase #2	$38.48	10.449%	$42.5008	$42.50	$42.50	$42.50
Purchase #3	$81.55	3.724%	$84.5869	$84.59	$84.60	$84.60
Purchase #4	$212.72	9.692%	$233.3368	$233.34	$233.35	$233.30
Purchase #5	$100.60	11.611%	$112.2807	$112.28	$112.30	$112.30
Purchase #6	$51.43	6.779%	$54.9164	$54.92	$54.90	$54.90
Purchase #7	$40.95	4.758%	$42.8984	$42.90	$42.90	$42.90
7 purchase totals =	$712.23		$773.4488	$773.46	$773.50	$773.40