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	$45.33	9.354%	$49.5702	$49.57	$49.55	$49.60
Purchase #2	$231.56	13.688%	$263.2559	$263.26	$263.25	$263.30
Purchase #3	$54.45	13.607%	$61.859	$61.86	$61.85	$61.90
Purchase #4	$188.86	8.334%	$204.5996	$204.60	$204.60	$204.60
Purchase #5	$105.73	3.570%	$109.5046	$109.50	$109.50	$109.50
Purchase #6	$87.83	8.237%	$95.0646	$95.06	$95.05	$95.10
Purchase #7	$80.41	13.408%	$91.1914	$91.19	$91.20	$91.20
7 purchase totals =	$794.17		$875.0453	$875.04	$875.00	$875.20