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	$172.73	9.261%	$188.7265	$188.73	$188.75	$188.70
Purchase #2	$80.34	5.749%	$84.9587	$84.96	$84.95	$85.00
Purchase #3	$181.82	5.178%	$191.2346	$191.23	$191.25	$191.20
Purchase #4	$50.64	12.829%	$57.1366	$57.14	$57.15	$57.10
Purchase #5	$115.68	13.611%	$131.4252	$131.43	$131.45	$131.40
Purchase #6	$245.29	5.695%	$259.2593	$259.26	$259.25	$259.30
Purchase #7	$125.51	13.196%	$142.0723	$142.07	$142.05	$142.10
7 purchase totals =	$972.01		$1,054.8132	$1,054.82	$1,054.85	$1,054.80