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	$210.88	13.242%	$238.8047	$238.80	$238.80	$238.80
Purchase #2	$192.25	10.265%	$211.9845	$211.98	$212.00	$212.00
Purchase #3	$111.28	7.369%	$119.4802	$119.48	$119.50	$119.50
Purchase #4	$84.90	13.435%	$96.3063	$96.31	$96.30	$96.30
Purchase #5	$48.30	12.614%	$54.3926	$54.39	$54.40	$54.40
Purchase #6	$134.33	11.256%	$149.4502	$149.45	$149.45	$149.50
Purchase #7	$72.36	13.839%	$82.3739	$82.37	$82.35	$82.40
7 purchase totals =	$854.30		$952.7924	$952.78	$952.80	$952.90