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	$81.39	13.636%	$92.4883	$92.49	$92.50	$92.50
Purchase #2	$174.82	3.620%	$181.1485	$181.15	$181.15	$181.10
Purchase #3	$66.77	8.510%	$72.4521	$72.45	$72.45	$72.50
Purchase #4	$145.80	13.470%	$165.4393	$165.44	$165.45	$165.40
Purchase #5	$193.85	5.737%	$204.9712	$204.97	$204.95	$205.00
Purchase #6	$204.95	4.356%	$213.8776	$213.88	$213.90	$213.90
Purchase #7	$117.54	8.461%	$127.4851	$127.49	$127.50	$127.50
7 purchase totals =	$985.12		$1,057.8621	$1,057.87	$1,057.90	$1,057.90