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	$162.80	10.458%	$179.8256	$179.83	$179.85	$179.80
Purchase #2	$77.71	5.656%	$82.1053	$82.11	$82.10	$82.10
Purchase #3	$83.59	10.788%	$92.6077	$92.61	$92.60	$92.60
Purchase #4	$108.88	7.777%	$117.3476	$117.35	$117.35	$117.30
Purchase #5	$124.25	10.379%	$137.1459	$137.15	$137.15	$137.10
Purchase #6	$98.70	13.146%	$111.6751	$111.68	$111.70	$111.70
Purchase #7	$108.62	4.352%	$113.3471	$113.35	$113.35	$113.30
7 purchase totals =	$764.55		$834.0543	$834.08	$834.10	$833.90