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	$147.86	13.172%	$167.3361	$167.34	$167.35	$167.30
Purchase #2	$188.72	3.248%	$194.8496	$194.85	$194.85	$194.80
Purchase #3	$201.32	9.671%	$220.7897	$220.79	$220.80	$220.80
Purchase #4	$249.29	11.470%	$277.8836	$277.88	$277.90	$277.90
Purchase #5	$97.77	5.135%	$102.7905	$102.79	$102.80	$102.80
Purchase #6	$134.89	6.653%	$143.8642	$143.86	$143.85	$143.90
Purchase #7	$39.49	8.524%	$42.8561	$42.86	$42.85	$42.90
7 purchase totals =	$1,059.34		$1,150.3698	$1,150.37	$1,150.40	$1,150.40