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	$26.86	3.695%	$27.8525	$27.85	$27.85	$27.90
Purchase #2	$40.38	7.502%	$43.4093	$43.41	$43.40	$43.40
Purchase #3	$107.35	5.230%	$112.9644	$112.96	$112.95	$113.00
Purchase #4	$75.37	9.407%	$82.4601	$82.46	$82.45	$82.50
Purchase #5	$73.61	11.476%	$82.0575	$82.06	$82.05	$82.10
Purchase #6	$152.96	3.852%	$158.852	$158.85	$158.85	$158.90
Purchase #7	$227.64	5.731%	$240.686	$240.69	$240.70	$240.70
7 purchase totals =	$704.17		$748.2818	$748.28	$748.25	$748.50