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	$189.71	5.412%	$199.9771	$199.98	$200.00	$200.00
Purchase #2	$196.31	10.184%	$216.3022	$216.30	$216.30	$216.30
Purchase #3	$66.88	8.618%	$72.6437	$72.64	$72.65	$72.60
Purchase #4	$127.30	13.776%	$144.8368	$144.84	$144.85	$144.80
Purchase #5	$237.99	10.714%	$263.4882	$263.49	$263.50	$263.50
Purchase #6	$121.35	5.400%	$127.9029	$127.90	$127.90	$127.90
Purchase #7	$117.97	7.555%	$126.8826	$126.88	$126.90	$126.90
7 purchase totals =	$1,057.51		$1,152.0335	$1,152.03	$1,152.10	$1,152.00