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	$149.54	12.869%	$168.7843	$168.78	$168.80	$168.80
Purchase #2	$156.37	8.557%	$169.7506	$169.75	$169.75	$169.80
Purchase #3	$115.59	7.525%	$124.2881	$124.29	$124.30	$124.30
Purchase #4	$43.47	3.344%	$44.9236	$44.92	$44.90	$44.90
Purchase #5	$141.53	6.175%	$150.2695	$150.27	$150.25	$150.30
Purchase #6	$214.27	6.824%	$228.8918	$228.89	$228.90	$228.90
Purchase #7	$163.73	13.336%	$185.565	$185.57	$185.55	$185.60
7 purchase totals =	$984.50		$1,072.4729	$1,072.47	$1,072.45	$1,072.60