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	$31.94	10.553%	$35.3106	$35.31	$35.30	$35.30
Purchase #2	$111.96	10.161%	$123.3363	$123.34	$123.35	$123.30
Purchase #3	$119.71	11.570%	$133.5604	$133.56	$133.55	$133.60
Purchase #4	$185.60	5.645%	$196.0771	$196.08	$196.10	$196.10
Purchase #5	$221.56	3.374%	$229.0354	$229.04	$229.05	$229.00
Purchase #6	$87.77	12.787%	$98.9931	$98.99	$99.00	$99.00
Purchase #7	$201.47	3.332%	$208.183	$208.18	$208.20	$208.20
7 purchase totals =	$960.01		$1,024.4959	$1,024.50	$1,024.55	$1,024.50