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	$15.67	8.341%	$16.977	$16.98	$17.00	$17.00
Purchase #2	$70.80	3.258%	$73.1067	$73.11	$73.10	$73.10
Purchase #3	$153.80	11.557%	$171.5747	$171.57	$171.55	$171.60
Purchase #4	$205.95	7.727%	$221.8638	$221.86	$221.85	$221.90
Purchase #5	$123.82	6.108%	$131.3829	$131.38	$131.40	$131.40
Purchase #6	$250.65	13.139%	$283.5829	$283.58	$283.60	$283.60
Purchase #7	$219.78	13.245%	$248.8899	$248.89	$248.90	$248.90
7 purchase totals =	$1,040.47		$1,147.3779	$1,147.37	$1,147.40	$1,147.50