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	$223.33	8.309%	$241.8865	$241.89	$241.90	$241.90
Purchase #2	$69.67	4.632%	$72.8971	$72.90	$72.90	$72.90
Purchase #3	$213.86	8.643%	$232.3439	$232.34	$232.35	$232.30
Purchase #4	$114.30	11.223%	$127.1279	$127.13	$127.15	$127.10
Purchase #5	$108.40	6.743%	$115.7094	$115.71	$115.70	$115.70
Purchase #6	$36.42	13.870%	$41.4715	$41.47	$41.45	$41.50
Purchase #7	$175.95	9.196%	$192.1304	$192.13	$192.15	$192.10
7 purchase totals =	$941.93		$1,023.5667	$1,023.57	$1,023.60	$1,023.50