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	$159.99	7.713%	$172.33	$172.33	$172.35	$172.30
Purchase #2	$79.39	4.453%	$82.9252	$82.93	$82.95	$82.90
Purchase #3	$180.50	5.476%	$190.3842	$190.38	$190.40	$190.40
Purchase #4	$124.31	7.688%	$133.867	$133.87	$133.85	$133.90
Purchase #5	$163.47	9.829%	$179.5375	$179.54	$179.55	$179.50
Purchase #6	$90.42	10.869%	$100.2477	$100.25	$100.25	$100.20
Purchase #7	$218.94	3.751%	$227.1524	$227.15	$227.15	$227.20
7 purchase totals =	$1,017.02		$1,086.4440	$1,086.45	$1,086.50	$1,086.40