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	$182.61	11.669%	$203.9188	$203.92	$203.90	$203.90
Purchase #2	$50.84	6.506%	$54.1477	$54.15	$54.15	$54.10
Purchase #3	$108.64	4.253%	$113.2605	$113.26	$113.25	$113.30
Purchase #4	$218.61	11.189%	$243.0703	$243.07	$243.05	$243.10
Purchase #5	$65.88	7.430%	$70.7749	$70.77	$70.75	$70.80
Purchase #6	$210.63	13.227%	$238.49	$238.49	$238.50	$238.50
Purchase #7	$81.51	13.842%	$92.7926	$92.79	$92.80	$92.80
7 purchase totals =	$918.72		$1,016.4548	$1,016.45	$1,016.40	$1,016.50