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	$78.98	13.234%	$89.4322	$89.43	$89.45	$89.40
Purchase #2	$104.98	12.428%	$118.0269	$118.03	$118.05	$118.00
Purchase #3	$247.27	8.381%	$267.9937	$267.99	$268.00	$268.00
Purchase #4	$181.62	4.626%	$190.0217	$190.02	$190.00	$190.00
Purchase #5	$141.89	10.576%	$156.8963	$156.90	$156.90	$156.90
Purchase #6	$133.84	6.287%	$142.2545	$142.25	$142.25	$142.30
Purchase #7	$168.35	11.322%	$187.4106	$187.41	$187.40	$187.40
7 purchase totals =	$1,056.93		$1,152.0359	$1,152.03	$1,152.05	$1,152.00