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	$79.90	7.408%	$85.819	$85.82	$85.80	$85.80
Purchase #2	$136.69	4.517%	$142.8643	$142.86	$142.85	$142.90
Purchase #3	$239.38	12.741%	$269.8794	$269.88	$269.90	$269.90
Purchase #4	$87.38	12.573%	$98.3663	$98.37	$98.35	$98.40
Purchase #5	$168.27	10.197%	$185.4285	$185.43	$185.45	$185.40
Purchase #6	$13.65	8.781%	$14.8486	$14.85	$14.85	$14.80
Purchase #7	$233.48	9.152%	$254.8481	$254.85	$254.85	$254.80
7 purchase totals =	$958.75		$1,052.0542	$1,052.06	$1,052.05	$1,052.00