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	$158.82	9.266%	$173.5363	$173.54	$173.55	$173.50
Purchase #2	$75.67	3.730%	$78.4925	$78.49	$78.50	$78.50
Purchase #3	$84.42	5.760%	$89.2826	$89.28	$89.30	$89.30
Purchase #4	$93.67	6.228%	$99.5038	$99.50	$99.50	$99.50
Purchase #5	$128.48	3.505%	$132.9832	$132.98	$133.00	$133.00
Purchase #6	$100.95	4.653%	$105.6472	$105.65	$105.65	$105.60
Purchase #7	$127.63	13.509%	$144.8715	$144.87	$144.85	$144.90
7 purchase totals =	$769.64		$824.3171	$824.31	$824.35	$824.30