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	$211.44	6.814%	$225.8475	$225.85	$225.85	$225.80
Purchase #2	$48.71	9.501%	$53.3379	$53.34	$53.35	$53.30
Purchase #3	$181.52	4.873%	$190.3655	$190.37	$190.35	$190.40
Purchase #4	$196.43	6.280%	$208.7658	$208.77	$208.75	$208.80
Purchase #5	$37.66	3.512%	$38.9826	$38.98	$39.00	$39.00
Purchase #6	$81.38	3.853%	$84.5156	$84.52	$84.50	$84.50
Purchase #7	$68.82	4.713%	$72.0635	$72.06	$72.05	$72.10
7 purchase totals =	$825.96		$873.8784	$873.89	$873.85	$873.90