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	$32.86	7.807%	$35.4254	$35.43	$35.45	$35.40
Purchase #2	$101.42	11.662%	$113.2476	$113.25	$113.25	$113.20
Purchase #3	$112.43	3.400%	$116.2526	$116.25	$116.25	$116.30
Purchase #4	$68.40	7.557%	$73.569	$73.57	$73.55	$73.60
Purchase #5	$103.60	7.825%	$111.7067	$111.71	$111.70	$111.70
Purchase #6	$179.86	10.829%	$199.337	$199.34	$199.35	$199.30
Purchase #7	$124.96	7.718%	$134.6044	$134.60	$134.60	$134.60
7 purchase totals =	$723.53		$784.1427	$784.15	$784.15	$784.10