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	$52.76	9.192%	$57.6097	$57.61	$57.60	$57.60
Purchase #2	$96.40	5.413%	$101.6181	$101.62	$101.60	$101.60
Purchase #3	$245.88	5.480%	$259.3542	$259.35	$259.35	$259.40
Purchase #4	$248.57	7.774%	$267.8938	$267.89	$267.90	$267.90
Purchase #5	$111.37	5.488%	$117.482	$117.48	$117.50	$117.50
Purchase #6	$104.86	13.102%	$118.5988	$118.60	$118.60	$118.60
Purchase #7	$87.72	7.318%	$94.1393	$94.14	$94.15	$94.10
7 purchase totals =	$947.56		$1,016.6959	$1,016.69	$1,016.70	$1,016.70