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	$184.51	8.539%	$200.2653	$200.27	$200.25	$200.30
Purchase #2	$167.37	11.321%	$186.318	$186.32	$186.30	$186.30
Purchase #3	$218.95	5.445%	$230.8718	$230.87	$230.85	$230.90
Purchase #4	$157.90	13.389%	$179.0412	$179.04	$179.05	$179.00
Purchase #5	$148.83	9.232%	$162.57	$162.57	$162.55	$162.60
Purchase #6	$142.51	12.856%	$160.8311	$160.83	$160.85	$160.80
Purchase #7	$167.73	3.664%	$173.8756	$173.88	$173.90	$173.90
7 purchase totals =	$1,187.80		$1,293.7730	$1,293.78	$1,293.75	$1,293.80