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	$110.80	5.434%	$116.8209	$116.82	$116.80	$116.80
Purchase #2	$19.45	10.704%	$21.5319	$21.53	$21.55	$21.50
Purchase #3	$29.72	6.736%	$31.7219	$31.72	$31.70	$31.70
Purchase #4	$167.57	3.213%	$172.954	$172.95	$172.95	$173.00
Purchase #5	$31.56	13.678%	$35.8768	$35.88	$35.90	$35.90
Purchase #6	$165.92	11.676%	$185.2928	$185.29	$185.30	$185.30
Purchase #7	$209.83	11.742%	$234.4682	$234.47	$234.45	$234.50
7 purchase totals =	$734.85		$798.6665	$798.66	$798.65	$798.70