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	$92.52	6.764%	$98.7781	$98.78	$98.80	$98.80
Purchase #2	$150.27	5.354%	$158.3155	$158.32	$158.30	$158.30
Purchase #3	$161.36	4.196%	$168.1307	$168.13	$168.15	$168.10
Purchase #4	$32.92	13.275%	$37.2901	$37.29	$37.30	$37.30
Purchase #5	$109.70	3.643%	$113.6964	$113.70	$113.70	$113.70
Purchase #6	$121.82	9.691%	$133.6256	$133.63	$133.65	$133.60
Purchase #7	$169.32	3.492%	$175.2327	$175.23	$175.25	$175.20
7 purchase totals =	$837.91		$885.0691	$885.08	$885.15	$885.00