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	$211.90	3.104%	$218.4774	$218.48	$218.50	$218.50
Purchase #2	$230.39	3.476%	$238.3984	$238.40	$238.40	$238.40
Purchase #3	$87.54	10.645%	$96.8586	$96.86	$96.85	$96.90
Purchase #4	$160.93	5.527%	$169.8246	$169.82	$169.80	$169.80
Purchase #5	$63.74	13.711%	$72.4794	$72.48	$72.50	$72.50
Purchase #6	$132.26	3.387%	$136.7396	$136.74	$136.75	$136.70
Purchase #7	$196.93	6.152%	$209.0451	$209.05	$209.05	$209.00
7 purchase totals =	$1,083.69		$1,141.8231	$1,141.83	$1,141.85	$1,141.80