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	$68.82	5.524%	$72.6216	$72.62	$72.60	$72.60
Purchase #2	$164.92	13.343%	$186.9253	$186.93	$186.95	$186.90
Purchase #3	$104.71	7.355%	$112.4114	$112.41	$112.40	$112.40
Purchase #4	$245.30	3.665%	$254.2902	$254.29	$254.30	$254.30
Purchase #5	$145.84	10.605%	$161.3063	$161.31	$161.30	$161.30
Purchase #6	$31.81	12.154%	$35.6762	$35.68	$35.70	$35.70
Purchase #7	$202.60	10.374%	$223.6177	$223.62	$223.60	$223.60
7 purchase totals =	$964.00		$1,046.8487	$1,046.86	$1,046.85	$1,046.80