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	$238.37	12.813%	$268.9123	$268.91	$268.90	$268.90
Purchase #2	$203.46	9.530%	$222.8497	$222.85	$222.85	$222.80
Purchase #3	$56.86	9.586%	$62.3106	$62.31	$62.30	$62.30
Purchase #4	$68.44	5.122%	$71.9455	$71.95	$71.95	$71.90
Purchase #5	$116.52	6.560%	$124.1637	$124.16	$124.15	$124.20
Purchase #6	$200.40	13.493%	$227.44	$227.44	$227.45	$227.40
Purchase #7	$83.91	12.488%	$94.3887	$94.39	$94.40	$94.40
7 purchase totals =	$967.96		$1,072.0105	$1,072.01	$1,072.00	$1,071.90