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	$72.95	11.619%	$81.4261	$81.43	$81.45	$81.40
Purchase #2	$220.81	9.799%	$242.4472	$242.45	$242.45	$242.40
Purchase #3	$247.60	6.539%	$263.7906	$263.79	$263.80	$263.80
Purchase #4	$109.28	4.791%	$114.5156	$114.52	$114.50	$114.50
Purchase #5	$132.48	10.501%	$146.3917	$146.39	$146.40	$146.40
Purchase #6	$23.80	7.260%	$25.5279	$25.53	$25.55	$25.50
Purchase #7	$216.72	4.508%	$226.4897	$226.49	$226.50	$226.50
7 purchase totals =	$1,023.64		$1,100.5888	$1,100.60	$1,100.65	$1,100.50