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	$219.44	11.355%	$244.3574	$244.36	$244.35	$244.40
Purchase #2	$42.40	7.817%	$45.7144	$45.71	$45.70	$45.70
Purchase #3	$175.77	6.300%	$186.8435	$186.84	$186.85	$186.80
Purchase #4	$38.62	4.135%	$40.2169	$40.22	$40.20	$40.20
Purchase #5	$212.72	12.148%	$238.5612	$238.56	$238.55	$238.60
Purchase #6	$158.48	3.448%	$163.9444	$163.94	$163.95	$163.90
Purchase #7	$20.89	4.603%	$21.8516	$21.85	$21.85	$21.90
7 purchase totals =	$868.32		$941.4894	$941.48	$941.45	$941.50