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	$86.43	3.366%	$89.3392	$89.34	$89.35	$89.30
Purchase #2	$38.78	12.155%	$43.4937	$43.49	$43.50	$43.50
Purchase #3	$191.51	10.227%	$211.0957	$211.10	$211.10	$211.10
Purchase #4	$151.62	3.608%	$157.0904	$157.09	$157.10	$157.10
Purchase #5	$27.53	7.167%	$29.5031	$29.50	$29.50	$29.50
Purchase #6	$44.46	3.666%	$46.0899	$46.09	$46.10	$46.10
Purchase #7	$98.96	4.173%	$103.0896	$103.09	$103.10	$103.10
7 purchase totals =	$639.29		$679.7016	$679.70	$679.75	$679.70