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	$31.95	5.346%	$33.658	$33.66	$33.65	$33.70
Purchase #2	$41.52	10.425%	$45.8485	$45.85	$45.85	$45.80
Purchase #3	$172.31	3.124%	$177.693	$177.69	$177.70	$177.70
Purchase #4	$227.76	6.764%	$243.1657	$243.17	$243.15	$243.20
Purchase #5	$83.82	3.238%	$86.5341	$86.53	$86.55	$86.50
Purchase #6	$116.35	6.419%	$123.8185	$123.82	$123.80	$123.80
Purchase #7	$246.32	7.423%	$264.6043	$264.60	$264.60	$264.60
7 purchase totals =	$920.03		$975.3221	$975.32	$975.30	$975.30