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	$103.32	11.216%	$114.9084	$114.91	$114.90	$114.90
Purchase #2	$241.75	9.204%	$264.0007	$264.00	$264.00	$264.00
Purchase #3	$176.93	11.218%	$196.778	$196.78	$196.80	$196.80
Purchase #4	$61.58	12.498%	$69.2763	$69.28	$69.30	$69.30
Purchase #5	$13.72	8.702%	$14.9139	$14.91	$14.90	$14.90
Purchase #6	$213.59	13.126%	$241.6258	$241.63	$241.65	$241.60
Purchase #7	$57.57	7.370%	$61.8129	$61.81	$61.80	$61.80
7 purchase totals =	$868.46		$963.3160	$963.32	$963.35	$963.30