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	$14.71	5.188%	$15.4732	$15.47	$15.45	$15.50
Purchase #2	$131.99	12.508%	$148.4993	$148.50	$148.50	$148.50
Purchase #3	$195.92	9.808%	$215.1358	$215.14	$215.15	$215.10
Purchase #4	$165.37	9.823%	$181.6143	$181.61	$181.60	$181.60
Purchase #5	$41.37	10.617%	$45.7623	$45.76	$45.75	$45.80
Purchase #6	$111.62	5.443%	$117.6955	$117.70	$117.70	$117.70
Purchase #7	$78.78	4.161%	$82.058	$82.06	$82.05	$82.10
7 purchase totals =	$739.76		$806.2384	$806.24	$806.20	$806.30