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	$99.47	6.167%	$105.6043	$105.60	$105.60	$105.60
Purchase #2	$114.47	4.267%	$119.3544	$119.35	$119.35	$119.40
Purchase #3	$137.65	11.300%	$153.2045	$153.20	$153.20	$153.20
Purchase #4	$244.61	11.375%	$272.4344	$272.43	$272.45	$272.40
Purchase #5	$67.43	9.275%	$73.6841	$73.68	$73.70	$73.70
Purchase #6	$115.48	3.513%	$119.5368	$119.54	$119.55	$119.50
Purchase #7	$153.32	9.287%	$167.5588	$167.56	$167.55	$167.60
7 purchase totals =	$932.43		$1,011.3773	$1,011.36	$1,011.40	$1,011.40