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	$85.76	8.324%	$92.8987	$92.90	$92.90	$92.90
Purchase #2	$190.29	5.562%	$200.8739	$200.87	$200.85	$200.90
Purchase #3	$61.68	3.594%	$63.8968	$63.90	$63.90	$63.90
Purchase #4	$75.82	5.708%	$80.1478	$80.15	$80.15	$80.10
Purchase #5	$102.88	12.396%	$115.633	$115.63	$115.65	$115.60
Purchase #6	$80.44	10.731%	$89.072	$89.07	$89.05	$89.10
Purchase #7	$82.52	3.439%	$85.3579	$85.36	$85.35	$85.40
7 purchase totals =	$679.39		$727.8801	$727.88	$727.85	$727.90