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	$215.66	10.648%	$238.6235	$238.62	$238.60	$238.60
Purchase #2	$247.36	5.102%	$259.9803	$259.98	$260.00	$260.00
Purchase #3	$163.32	6.717%	$174.2902	$174.29	$174.30	$174.30
Purchase #4	$245.51	7.537%	$264.0141	$264.01	$264.00	$264.00
Purchase #5	$68.45	5.754%	$72.3886	$72.39	$72.40	$72.40
Purchase #6	$64.29	11.326%	$71.5715	$71.57	$71.55	$71.60
Purchase #7	$193.77	11.150%	$215.3754	$215.38	$215.40	$215.40
7 purchase totals =	$1,198.36		$1,296.2436	$1,296.24	$1,296.25	$1,296.30