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	$200.43	5.835%	$212.1251	$212.13	$212.15	$212.10
Purchase #2	$162.78	11.637%	$181.7227	$181.72	$181.70	$181.70
Purchase #3	$11.64	9.662%	$12.7647	$12.76	$12.75	$12.80
Purchase #4	$240.45	5.638%	$254.0066	$254.01	$254.00	$254.00
Purchase #5	$241.69	12.145%	$271.0433	$271.04	$271.05	$271.00
Purchase #6	$80.44	13.292%	$91.1321	$91.13	$91.15	$91.10
Purchase #7	$54.80	9.270%	$59.88	$59.88	$59.90	$59.90
7 purchase totals =	$992.23		$1,082.6745	$1,082.67	$1,082.70	$1,082.60