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	$80.92	6.108%	$85.8626	$85.86	$85.85	$85.90
Purchase #2	$102.83	9.794%	$112.9012	$112.90	$112.90	$112.90
Purchase #3	$64.99	4.804%	$68.1121	$68.11	$68.10	$68.10
Purchase #4	$250.27	10.648%	$276.9187	$276.92	$276.90	$276.90
Purchase #5	$218.33	9.713%	$239.5364	$239.54	$239.55	$239.50
Purchase #6	$163.83	6.769%	$174.9197	$174.92	$174.90	$174.90
Purchase #7	$91.67	12.680%	$103.2938	$103.29	$103.30	$103.30
7 purchase totals =	$972.84		$1,061.5445	$1,061.54	$1,061.50	$1,061.50