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	$72.31	11.418%	$80.5664	$80.57	$80.55	$80.60
Purchase #2	$65.96	10.108%	$72.6272	$72.63	$72.65	$72.60
Purchase #3	$176.45	10.824%	$195.5489	$195.55	$195.55	$195.50
Purchase #4	$192.37	8.317%	$208.3694	$208.37	$208.35	$208.40
Purchase #5	$114.48	11.543%	$127.6944	$127.69	$127.70	$127.70
Purchase #6	$77.44	7.629%	$83.3479	$83.35	$83.35	$83.30
Purchase #7	$62.31	4.678%	$65.2249	$65.22	$65.20	$65.20
7 purchase totals =	$761.32		$833.3791	$833.38	$833.35	$833.30