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	$206.63	4.297%	$215.5089	$215.51	$215.50	$215.50
Purchase #2	$172.51	10.793%	$191.129	$191.13	$191.15	$191.10
Purchase #3	$68.80	5.526%	$72.6019	$72.60	$72.60	$72.60
Purchase #4	$148.77	4.114%	$154.8904	$154.89	$154.90	$154.90
Purchase #5	$166.58	12.611%	$187.5874	$187.59	$187.60	$187.60
Purchase #6	$153.33	11.427%	$170.851	$170.85	$170.85	$170.90
Purchase #7	$231.31	3.540%	$239.4984	$239.50	$239.50	$239.50
7 purchase totals =	$1,147.93		$1,232.0670	$1,232.07	$1,232.10	$1,232.10