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	$133.38	13.801%	$151.7878	$151.79	$151.80	$151.80
Purchase #2	$176.97	13.442%	$200.7583	$200.76	$200.75	$200.80
Purchase #3	$51.36	6.707%	$54.8047	$54.80	$54.80	$54.80
Purchase #4	$38.57	11.750%	$43.102	$43.10	$43.10	$43.10
Purchase #5	$133.87	12.582%	$150.7135	$150.71	$150.70	$150.70
Purchase #6	$88.76	12.583%	$99.9287	$99.93	$99.95	$99.90
Purchase #7	$99.32	3.159%	$102.4575	$102.46	$102.45	$102.50
7 purchase totals =	$722.23		$803.5525	$803.55	$803.55	$803.60