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	$131.60	4.280%	$137.2325	$137.23	$137.25	$137.20
Purchase #2	$233.72	8.255%	$253.0136	$253.01	$253.00	$253.00
Purchase #3	$39.82	5.827%	$42.1403	$42.14	$42.15	$42.10
Purchase #4	$110.43	5.160%	$116.1282	$116.13	$116.15	$116.10
Purchase #5	$61.93	8.781%	$67.3681	$67.37	$67.35	$67.40
Purchase #6	$140.95	13.525%	$160.0135	$160.01	$160.00	$160.00
Purchase #7	$168.65	12.390%	$189.5457	$189.55	$189.55	$189.50
7 purchase totals =	$887.10		$965.4419	$965.44	$965.45	$965.30