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	$63.47	11.486%	$70.7602	$70.76	$70.75	$70.80
Purchase #2	$226.28	3.123%	$233.3467	$233.35	$233.35	$233.30
Purchase #3	$156.73	11.568%	$174.8605	$174.86	$174.85	$174.90
Purchase #4	$95.43	7.504%	$102.5911	$102.59	$102.60	$102.60
Purchase #5	$58.63	9.645%	$64.2849	$64.28	$64.30	$64.30
Purchase #6	$68.39	12.268%	$76.7801	$76.78	$76.80	$76.80
Purchase #7	$40.42	7.698%	$43.5315	$43.53	$43.55	$43.50
7 purchase totals =	$709.35		$766.1550	$766.15	$766.20	$766.20