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	$67.93	4.542%	$71.0154	$71.02	$71.00	$71.00
Purchase #2	$17.41	10.633%	$19.2612	$19.26	$19.25	$19.30
Purchase #3	$56.35	13.324%	$63.8581	$63.86	$63.85	$63.90
Purchase #4	$81.64	9.478%	$89.3778	$89.38	$89.40	$89.40
Purchase #5	$125.43	13.112%	$141.8764	$141.88	$141.90	$141.90
Purchase #6	$80.31	4.772%	$84.1424	$84.14	$84.15	$84.10
Purchase #7	$171.77	13.834%	$195.5327	$195.53	$195.55	$195.50
7 purchase totals =	$600.84		$665.0640	$665.07	$665.10	$665.10