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	$213.46	8.410%	$231.412	$231.41	$231.40	$231.40
Purchase #2	$57.85	7.483%	$62.1789	$62.18	$62.20	$62.20
Purchase #3	$178.31	9.623%	$195.4688	$195.47	$195.45	$195.50
Purchase #4	$105.44	6.116%	$111.8887	$111.89	$111.90	$111.90
Purchase #5	$112.64	6.590%	$120.063	$120.06	$120.05	$120.10
Purchase #6	$142.41	4.256%	$148.471	$148.47	$148.45	$148.50
Purchase #7	$68.52	13.150%	$77.5304	$77.53	$77.55	$77.50
7 purchase totals =	$878.63		$947.0128	$947.01	$947.00	$947.10