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	$241.29	11.523%	$269.0938	$269.09	$269.10	$269.10
Purchase #2	$136.83	7.419%	$146.9814	$146.98	$147.00	$147.00
Purchase #3	$95.48	6.566%	$101.7492	$101.75	$101.75	$101.70
Purchase #4	$108.50	6.740%	$115.8129	$115.81	$115.80	$115.80
Purchase #5	$85.33	6.116%	$90.5488	$90.55	$90.55	$90.50
Purchase #6	$218.92	13.475%	$248.4195	$248.42	$248.40	$248.40
Purchase #7	$100.71	13.614%	$114.4207	$114.42	$114.40	$114.40
7 purchase totals =	$987.06		$1,087.0263	$1,087.02	$1,087.00	$1,086.90