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	$143.92	12.812%	$162.359	$162.36	$162.35	$162.40
Purchase #2	$12.36	12.778%	$13.9394	$13.94	$13.95	$13.90
Purchase #3	$85.68	13.132%	$96.9315	$96.93	$96.95	$96.90
Purchase #4	$89.54	5.405%	$94.3796	$94.38	$94.40	$94.40
Purchase #5	$106.54	4.183%	$110.9966	$111.00	$111.00	$111.00
Purchase #6	$186.37	11.827%	$208.412	$208.41	$208.40	$208.40
Purchase #7	$62.50	6.502%	$66.5638	$66.56	$66.55	$66.60
7 purchase totals =	$686.91		$753.5819	$753.58	$753.60	$753.60