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	$245.71	6.637%	$262.0178	$262.02	$262.00	$262.00
Purchase #2	$151.73	11.138%	$168.6297	$168.63	$168.65	$168.60
Purchase #3	$125.89	13.298%	$142.6309	$142.63	$142.65	$142.60
Purchase #4	$213.36	4.533%	$223.0316	$223.03	$223.05	$223.00
Purchase #5	$61.46	7.404%	$66.0105	$66.01	$66.00	$66.00
Purchase #6	$242.33	10.724%	$268.3175	$268.32	$268.30	$268.30
Purchase #7	$116.52	10.188%	$128.3911	$128.39	$128.40	$128.40
7 purchase totals =	$1,157.00		$1,259.0291	$1,259.03	$1,259.05	$1,258.90