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	$10.76	4.276%	$11.2201	$11.22	$11.20	$11.20
Purchase #2	$77.59	5.757%	$82.0569	$82.06	$82.05	$82.10
Purchase #3	$187.84	9.697%	$206.0548	$206.05	$206.05	$206.10
Purchase #4	$51.61	7.539%	$55.5009	$55.50	$55.50	$55.50
Purchase #5	$224.45	7.343%	$240.9314	$240.93	$240.95	$240.90
Purchase #6	$77.46	13.747%	$88.1084	$88.11	$88.10	$88.10
Purchase #7	$102.73	13.496%	$116.5944	$116.59	$116.60	$116.60
7 purchase totals =	$732.44		$800.4669	$800.46	$800.45	$800.50