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	$77.39	4.710%	$81.0351	$81.04	$81.05	$81.00
Purchase #2	$171.90	5.620%	$181.5608	$181.56	$181.55	$181.60
Purchase #3	$156.82	5.269%	$165.0828	$165.08	$165.10	$165.10
Purchase #4	$69.50	4.511%	$72.6351	$72.64	$72.65	$72.60
Purchase #5	$180.77	6.757%	$192.9846	$192.98	$193.00	$193.00
Purchase #6	$182.63	4.108%	$190.1324	$190.13	$190.15	$190.10
Purchase #7	$142.97	5.501%	$150.8348	$150.83	$150.85	$150.80
7 purchase totals =	$981.98		$1,034.2656	$1,034.26	$1,034.35	$1,034.20