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	$117.87	11.233%	$131.1103	$131.11	$131.10	$131.10
Purchase #2	$98.82	12.714%	$111.384	$111.38	$111.40	$111.40
Purchase #3	$76.96	3.870%	$79.9384	$79.94	$79.95	$79.90
Purchase #4	$176.97	5.262%	$186.2822	$186.28	$186.30	$186.30
Purchase #5	$99.91	10.216%	$110.1168	$110.12	$110.10	$110.10
Purchase #6	$171.76	8.647%	$186.6121	$186.61	$186.60	$186.60
Purchase #7	$205.47	9.291%	$224.5602	$224.56	$224.55	$224.60
7 purchase totals =	$947.76		$1,030.0040	$1,030.00	$1,030.00	$1,030.00