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	$182.33	8.786%	$198.3495	$198.35	$198.35	$198.30
Purchase #2	$87.69	11.771%	$98.012	$98.01	$98.00	$98.00
Purchase #3	$31.31	13.683%	$35.5941	$35.59	$35.60	$35.60
Purchase #4	$173.88	6.813%	$185.7264	$185.73	$185.75	$185.70
Purchase #5	$233.55	9.474%	$255.6765	$255.68	$255.70	$255.70
Purchase #6	$37.71	3.410%	$38.9959	$39.00	$39.00	$39.00
Purchase #7	$230.98	9.588%	$253.1264	$253.13	$253.15	$253.10
7 purchase totals =	$977.45		$1,065.4808	$1,065.49	$1,065.55	$1,065.40