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	$53.43	8.214%	$57.8187	$57.82	$57.80	$57.80
Purchase #2	$130.83	8.509%	$141.9623	$141.96	$141.95	$142.00
Purchase #3	$82.58	3.417%	$85.4018	$85.40	$85.40	$85.40
Purchase #4	$35.32	11.297%	$39.3101	$39.31	$39.30	$39.30
Purchase #5	$89.73	5.118%	$94.3224	$94.32	$94.30	$94.30
Purchase #6	$5.32	10.845%	$5.897	$5.90	$5.90	$5.90
Purchase #7	$64.27	13.336%	$72.841	$72.84	$72.85	$72.80
7 purchase totals =	$461.48		$497.5533	$497.55	$497.50	$497.50