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	$155.96	11.724%	$174.2448	$174.24	$174.25	$174.20
Purchase #2	$117.54	11.577%	$131.1476	$131.15	$131.15	$131.10
Purchase #3	$236.38	10.406%	$260.9777	$260.98	$261.00	$261.00
Purchase #4	$103.26	6.171%	$109.6322	$109.63	$109.65	$109.60
Purchase #5	$54.47	9.772%	$59.7928	$59.79	$59.80	$59.80
Purchase #6	$88.85	4.624%	$92.9584	$92.96	$92.95	$93.00
Purchase #7	$214.94	9.289%	$234.9058	$234.91	$234.90	$234.90
7 purchase totals =	$971.40		$1,063.6593	$1,063.66	$1,063.70	$1,063.60