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	$14.75	11.407%	$16.4325	$16.43	$16.45	$16.40
Purchase #2	$77.80	6.133%	$82.5715	$82.57	$82.55	$82.60
Purchase #3	$239.41	6.658%	$255.3499	$255.35	$255.35	$255.30
Purchase #4	$240.59	12.183%	$269.9011	$269.90	$269.90	$269.90
Purchase #5	$76.33	11.823%	$85.3545	$85.35	$85.35	$85.40
Purchase #6	$196.98	11.612%	$219.8533	$219.85	$219.85	$219.90
Purchase #7	$79.76	4.184%	$83.0972	$83.10	$83.10	$83.10
7 purchase totals =	$925.62		$1,012.5600	$1,012.55	$1,012.55	$1,012.60