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	$95.93	8.380%	$103.9689	$103.97	$103.95	$104.00
Purchase #2	$90.96	7.502%	$97.7838	$97.78	$97.80	$97.80
Purchase #3	$103.79	7.651%	$111.731	$111.73	$111.75	$111.70
Purchase #4	$138.30	9.423%	$151.332	$151.33	$151.35	$151.30
Purchase #5	$93.86	8.820%	$102.1385	$102.14	$102.15	$102.10
Purchase #6	$185.39	8.166%	$200.5289	$200.53	$200.55	$200.50
Purchase #7	$84.89	5.211%	$89.3136	$89.31	$89.30	$89.30
7 purchase totals =	$793.12		$856.7967	$856.79	$856.85	$856.70