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	$56.62	9.187%	$61.8217	$61.82	$61.80	$61.80
Purchase #2	$81.54	12.340%	$91.602	$91.60	$91.60	$91.60
Purchase #3	$236.84	4.403%	$247.2681	$247.27	$247.25	$247.30
Purchase #4	$71.90	11.470%	$80.1469	$80.15	$80.15	$80.10
Purchase #5	$143.46	8.428%	$155.5508	$155.55	$155.55	$155.60
Purchase #6	$7.86	8.514%	$8.5292	$8.53	$8.55	$8.50
Purchase #7	$91.29	5.786%	$96.572	$96.57	$96.55	$96.60
7 purchase totals =	$689.51		$741.4907	$741.49	$741.45	$741.50