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	$89.82	5.798%	$95.0278	$95.03	$95.05	$95.00
Purchase #2	$80.25	13.246%	$90.8799	$90.88	$90.90	$90.90
Purchase #3	$58.66	10.670%	$64.919	$64.92	$64.90	$64.90
Purchase #4	$138.95	12.512%	$156.3354	$156.34	$156.35	$156.30
Purchase #5	$71.58	7.657%	$77.0609	$77.06	$77.05	$77.10
Purchase #6	$72.85	6.642%	$77.6887	$77.69	$77.70	$77.70
Purchase #7	$128.46	12.112%	$144.0191	$144.02	$144.00	$144.00
7 purchase totals =	$640.57		$705.9308	$705.94	$705.95	$705.90