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	$240.85	9.181%	$262.9624	$262.96	$262.95	$263.00
Purchase #2	$83.32	7.753%	$89.7798	$89.78	$89.80	$89.80
Purchase #3	$158.46	3.506%	$164.0156	$164.02	$164.00	$164.00
Purchase #4	$14.53	8.512%	$15.7668	$15.77	$15.75	$15.80
Purchase #5	$68.32	6.182%	$72.5435	$72.54	$72.55	$72.50
Purchase #6	$158.57	3.621%	$164.3118	$164.31	$164.30	$164.30
Purchase #7	$31.88	11.186%	$35.4461	$35.45	$35.45	$35.40
7 purchase totals =	$755.93		$804.8260	$804.83	$804.80	$804.80