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	$26.90	8.816%	$29.2715	$29.27	$29.25	$29.30
Purchase #2	$79.93	8.302%	$86.5658	$86.57	$86.55	$86.60
Purchase #3	$183.35	7.118%	$196.4009	$196.40	$196.40	$196.40
Purchase #4	$33.77	3.681%	$35.0131	$35.01	$35.00	$35.00
Purchase #5	$240.27	13.656%	$273.0813	$273.08	$273.10	$273.10
Purchase #6	$156.74	10.824%	$173.7055	$173.71	$173.70	$173.70
Purchase #7	$239.66	6.575%	$255.4176	$255.42	$255.40	$255.40
7 purchase totals =	$960.62		$1,049.4557	$1,049.46	$1,049.40	$1,049.50