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	$130.72	9.228%	$142.7828	$142.78	$142.80	$142.80
Purchase #2	$245.75	7.641%	$264.5278	$264.53	$264.55	$264.50
Purchase #3	$142.75	7.148%	$152.9538	$152.95	$152.95	$153.00
Purchase #4	$139.50	9.247%	$152.3996	$152.40	$152.40	$152.40
Purchase #5	$245.60	13.332%	$278.3434	$278.34	$278.35	$278.30
Purchase #6	$171.37	6.638%	$182.7455	$182.75	$182.75	$182.70
Purchase #7	$147.80	13.571%	$167.8579	$167.86	$167.85	$167.90
7 purchase totals =	$1,223.49		$1,341.6108	$1,341.61	$1,341.65	$1,341.60