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	$54.27	10.391%	$59.9092	$59.91	$59.90	$59.90
Purchase #2	$233.70	6.316%	$248.4605	$248.46	$248.45	$248.50
Purchase #3	$248.72	5.541%	$262.5016	$262.50	$262.50	$262.50
Purchase #4	$116.59	12.230%	$130.849	$130.85	$130.85	$130.80
Purchase #5	$141.59	4.537%	$148.0139	$148.01	$148.00	$148.00
Purchase #6	$105.97	3.413%	$109.5868	$109.59	$109.60	$109.60
Purchase #7	$186.88	9.701%	$205.0092	$205.01	$205.00	$205.00
7 purchase totals =	$1,087.72		$1,164.3302	$1,164.33	$1,164.30	$1,164.30