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	$99.59	3.342%	$102.9183	$102.92	$102.90	$102.90
Purchase #2	$29.56	6.629%	$31.5195	$31.52	$31.50	$31.50
Purchase #3	$204.42	5.438%	$215.5364	$215.54	$215.55	$215.50
Purchase #4	$246.52	11.771%	$275.5379	$275.54	$275.55	$275.50
Purchase #5	$148.97	11.839%	$166.6066	$166.61	$166.60	$166.60
Purchase #6	$193.81	11.540%	$216.1757	$216.18	$216.20	$216.20
Purchase #7	$198.79	9.260%	$217.198	$217.20	$217.20	$217.20
7 purchase totals =	$1,121.66		$1,225.4924	$1,225.51	$1,225.50	$1,225.40