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	$164.77	11.853%	$184.3002	$184.30	$184.30	$184.30
Purchase #2	$136.94	10.667%	$151.5474	$151.55	$151.55	$151.50
Purchase #3	$155.83	4.528%	$162.886	$162.89	$162.90	$162.90
Purchase #4	$248.31	6.638%	$264.7928	$264.79	$264.80	$264.80
Purchase #5	$225.70	9.205%	$246.4757	$246.48	$246.50	$246.50
Purchase #6	$139.69	8.258%	$151.2256	$151.23	$151.25	$151.20
Purchase #7	$92.92	6.473%	$98.9347	$98.93	$98.95	$98.90
7 purchase totals =	$1,164.16		$1,260.1624	$1,260.17	$1,260.25	$1,260.10