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	$136.65	5.408%	$144.04	$144.04	$144.05	$144.00
Purchase #2	$170.48	8.356%	$184.7253	$184.73	$184.75	$184.70
Purchase #3	$205.73	9.468%	$225.2085	$225.21	$225.20	$225.20
Purchase #4	$99.35	4.212%	$103.5346	$103.53	$103.55	$103.50
Purchase #5	$178.78	4.396%	$186.6392	$186.64	$186.65	$186.60
Purchase #6	$148.96	12.691%	$167.8645	$167.86	$167.85	$167.90
Purchase #7	$53.78	12.656%	$60.5864	$60.59	$60.60	$60.60
7 purchase totals =	$993.73		$1,072.5985	$1,072.60	$1,072.65	$1,072.50