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	$113.97	8.607%	$123.7794	$123.78	$123.80	$123.80
Purchase #2	$209.84	13.102%	$237.3332	$237.33	$237.35	$237.30
Purchase #3	$148.86	4.581%	$155.6793	$155.68	$155.70	$155.70
Purchase #4	$40.27	3.592%	$41.7165	$41.72	$41.70	$41.70
Purchase #5	$87.64	13.589%	$99.5494	$99.55	$99.55	$99.50
Purchase #6	$143.86	8.337%	$155.8536	$155.85	$155.85	$155.90
Purchase #7	$205.54	9.444%	$224.9512	$224.95	$224.95	$225.00
7 purchase totals =	$949.98		$1,038.8626	$1,038.86	$1,038.90	$1,038.90