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	$193.39	7.839%	$208.5498	$208.55	$208.55	$208.50
Purchase #2	$243.85	12.725%	$274.8799	$274.88	$274.90	$274.90
Purchase #3	$128.36	11.821%	$143.5334	$143.53	$143.55	$143.50
Purchase #4	$158.40	12.738%	$178.577	$178.58	$178.60	$178.60
Purchase #5	$51.52	11.540%	$57.4654	$57.47	$57.45	$57.50
Purchase #6	$218.50	10.799%	$242.0958	$242.10	$242.10	$242.10
Purchase #7	$73.28	8.406%	$79.4399	$79.44	$79.45	$79.40
7 purchase totals =	$1,067.30		$1,184.5412	$1,184.55	$1,184.60	$1,184.50