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	$186.45	13.397%	$211.4287	$211.43	$211.45	$211.40
Purchase #2	$247.68	7.140%	$265.3644	$265.36	$265.35	$265.40
Purchase #3	$213.84	5.577%	$225.7659	$225.77	$225.75	$225.80
Purchase #4	$101.64	9.426%	$111.2206	$111.22	$111.20	$111.20
Purchase #5	$137.80	10.713%	$152.5625	$152.56	$152.55	$152.60
Purchase #6	$78.36	13.395%	$88.8563	$88.86	$88.85	$88.90
Purchase #7	$20.56	7.850%	$22.174	$22.17	$22.15	$22.20
7 purchase totals =	$986.33		$1,077.3724	$1,077.37	$1,077.30	$1,077.50