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	$174.74	12.252%	$196.1491	$196.15	$196.15	$196.10
Purchase #2	$219.78	13.704%	$249.8987	$249.90	$249.90	$249.90
Purchase #3	$49.90	5.812%	$52.8002	$52.80	$52.80	$52.80
Purchase #4	$171.45	4.669%	$179.455	$179.46	$179.45	$179.50
Purchase #5	$217.52	8.314%	$235.6046	$235.60	$235.60	$235.60
Purchase #6	$164.75	8.605%	$178.9267	$178.93	$178.95	$178.90
Purchase #7	$86.44	5.714%	$91.3792	$91.38	$91.40	$91.40
7 purchase totals =	$1,084.58		$1,184.2135	$1,184.22	$1,184.25	$1,184.20