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	$49.76	9.792%	$54.6325	$54.63	$54.65	$54.60
Purchase #2	$139.63	13.219%	$158.0877	$158.09	$158.10	$158.10
Purchase #3	$75.36	9.384%	$82.4318	$82.43	$82.45	$82.40
Purchase #4	$92.40	7.463%	$99.2958	$99.30	$99.30	$99.30
Purchase #5	$143.58	3.508%	$148.6168	$148.62	$148.60	$148.60
Purchase #6	$104.98	5.393%	$110.6416	$110.64	$110.65	$110.60
Purchase #7	$61.38	3.657%	$63.6247	$63.62	$63.60	$63.60
7 purchase totals =	$667.09		$717.3309	$717.33	$717.35	$717.20