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	$238.33	9.521%	$261.0214	$261.02	$261.00	$261.00
Purchase #2	$223.54	11.329%	$248.8648	$248.86	$248.85	$248.90
Purchase #3	$40.57	7.379%	$43.5637	$43.56	$43.55	$43.60
Purchase #4	$39.33	13.125%	$44.4921	$44.49	$44.50	$44.50
Purchase #5	$129.27	9.530%	$141.5894	$141.59	$141.60	$141.60
Purchase #6	$115.96	10.764%	$128.4419	$128.44	$128.45	$128.40
Purchase #7	$124.96	13.453%	$141.7709	$141.77	$141.75	$141.80
7 purchase totals =	$911.96		$1,009.7442	$1,009.73	$1,009.70	$1,009.80